Keywords

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Writing a work and acknowledging that it is poor after it is finished is one of the tragedies of the soul. Especially when it has to be acknowledged that this work is the best that could be done. (Fernando Pessoa, O livro do desassossego, São Paulo, Companhia das Letras, 1999, p. 230)

Legal certainty is a normative ideal of the first magnitude in any legal order, and particularly in the Brazilian order. Its importance is even greater in the field of tax law: The ideals protected by legal certainty have special relevance in the tax subsystem and a more protective significance by virtue of the existence of specific and emphatic norms in the National Tax System that act as instruments to guarantee the intelligibility of law through via the determinability of incidence hypotheses (the legality rule and the system of competence rules), the reliability of law through stability over time (the rule restricting the regulation of prescription and limitation to supplementary laws), period of validity (the rule prohibiting retroactivity) and procedure (rules that expressly apply rights and guarantees not specified in the tax subsystem, such as protection for acquired rights, completed legal acts and res iudicata), and the calculability of law through non-surprise (the anteriority rule).

The essential point is that the Brazilian Constitution, more than requiring the promotion of the legal certainty principle, embodies this principle, by virtue of its concern from beginning to end with the ideals of normative knowability, reliability and calculability, such is the emphasis it places on the limitation of power, especially the power to tax, and on fundamental rights and guarantees, particularly in tax law. However, these ideals cannot be even discerned, let alone realized, without progressive reduction of their indeterminacy. The efficacy of a legal principle, particularly the tax law certainty principle, results not from the proclamation of its ideals but from analytical decomposition of the dimensions, aspects and elements that make it up. Above all, a legal principle is a norm in need of conceptual decomposition. Unless it is “unwrapped” and its several constituent parts are disaggregated, its nature, proportions, functions and relations cannot be known. In this process of reduction to simple elements, however, it is crucial to develop a new understanding not only of the legal certainty principle but of the very definition of law, and its claim to certainty, to be the means whereby certainty is realized, or within which certainty is to be guaranteed.

The idea that law is a previously given object whose existence is totally independent of the activities relating to its application has given rise to a tendency to examine legal certainty almost exclusively from the angle of the requirement of determinate normative hypotheses, resulting in the idolization of the so-called principle of closed typicality in tax law. However, this understanding has restricted the discussion of legal certainty to factors that are unquestionably important but solely linked to the structure of language, leading to endless wrangling about determinacy, and consequently to unflagging debates about whether legal certainty can ever supply determinacy.

This perception of legal certainty, which centers on normative determinacy, ought to give way to an understanding founded on semantic-argumentative controllability. On this view, it ceases to be a property of law, and becomes something to be sought in law through processes of normative legitimation, determination, argumentation and justification, all of which are capable of addressing the problems ontologically inherent in law – problems of evidence, qualification, interpretation and relevance. What is at stake, more than certain law, is a right to legal certainty, not as something given by normative provisions – as if it were only an object to be simply revealed through a discoursive method circumscribed to a description of language – but as something to be sought through a metadiscoursive method that organizes and structures the experience of using language. From this perspective, legal certainty ceases to be a guarantee of content to be found through exclusively linguistic factors, and becomes a guarantee of respect to be constructed through semantic-argumentative elements.

It is precisely under this novel signification that legal certainty is most clearly revealed as an instrument to realize the values of freedom, equality and dignity: freedom because the more citizen taxpayers are assured of material and intellectual access to the norms they must obey, and the greater the stability of those norms, the better citizens will be able to grasp the present and plan for the future; equality because the more general and abstract the norms and the more uniformly they are applied, the more equally will citizen taxpayers be treated; dignity because the more accessible and stable the norms, and the sounder the justification for their application, the more intensely will citizen taxpayers be treated as being able to define themselves autonomously, both by present respect for the autonomy they have exercised in the past and by future respect for the autonomy they exercise in the present. In the field of tax law, this understanding evidences that legal certainty is an indispensable instrument for the realization of the principles of freedom, especially the freedom to exercise economic activities, equality and human dignity. Thus the legal certainty principle is the principle of respect for taxpayers as citizens.

According to this resignification, legal certainty is not consummated as a straight line or point, but as a range or spectrum of gradual realization. This graduality is not uniform or one-way, however: The overarching ideal (legal certainty) is the sum of partial ideals (normative knowability, reliability and calculability). These partial ideals can interact in the same direction as well as in different directions, so that, for example, the protection of certainty from one angle (as the pursuit of reliability through the stability of normative acts) may cause loss of certainty from another perspective (as the pursuit of calculability through the bindingness of normative acts). It should be noted that each partial ideal can be analyzed from different perspectives. For example, the intelligibility of the legal order can be analyzed for society in general or for practitioners of law; relative to the past, present or future; and so on. Thus each partial ideal needs an average analysis of its internally related subelements.

Consequently, legal certainty is always the result of an analysis of several factors from more than one perspective. It is a matter of a principle that determines the realization not of a uniform but of a non-uniform state, so that the interpreter must first decompose these elements and then gauge them in order to verify whether they can be promoted to a greater or lesser extent as a totality. The lack of such an investigation easily allows legal uncertainty to arise in the name of legal certainty. Hence the repeated emphasis in this book from beginning to end that legal certainty is either whole or not certainty. The judge must first examine each of the elements in their various dimensions and then verify whether it is being promoted more than restricted.

These considerations show that the legal certainty principle is only superficially a mere formal principle in a derogatory sense, i.e. decoupled from fundamental substantive principles. In reality it is a normative precondition for the efficacy of the order of principles, especially those that concern the development of the person as a rational and autonomous being. The legal certainty principle acts as a foundation for the validity of other legal norms and instrumentalizes their efficacy. Hence it is the norm of norms and their structural constraint. However, the foundational and instrumentalizing functions refer not only to the static aspects of norms but also to their dynamic aspects, which relate both to the transition from past to present and from present to future, and, most importantly, to the transition from the abstract level to the concrete level of the application of law.

In its requirement of knowability, the legal certainty principle serves as an instrument of guidance for taxpayers, so that they do not act mistakenly when they abide by the laws. In its ideal of reliability, it serves to assure the stability of law and its concretizations, preserving the past in the present and preventing taxpayers from being frustrated by what they have done. And in its objective of calculability, it favors the continuity of law, protecting the future in the present and preventing taxpayers from being surprised by what they do. Thus by aiming to avert mistakes, frustration and surprise, the legal certainty principle embodies the ideal of respect for the taxpayer. However, this ideal can be realized only through the intelligibility, loyalty and smoothness of state actions. These ideals in aggregate materialize a higher ideal of state moderation. The legal certainty principle therefore requires respect for taxpayers’ actions through state moderation.

However, respect for taxpayers is not enough, They must perceive themselves as being respected and act argumentatively on this respectability. In this regard, the legal certainty principle surpasses its essential function of assuring respect for individual action to become an instrument of respect for the argumentation citizens use to face problems relating to their actions in terms of evidence, qualification, interpretation and relevance. Thus it is clear that the tax law certainty principle is the principle that guarantees the respectability of citizen taxpayers’ actions and argumentation, requiring transparent respectability of taxpayers’ actions and the pertinent argumentation through state moderation. This moderation, in turn, requires that taxpayers be treated as rational, free and autonomous human beings, i.e. as citizens. Only then can they be legally oriented to conceive the present and shape the future. The legal certainty principle is, so to speak, the legal face of human dignity which, in requiring a visibly respectful transition from past to present and from present to future, prevents law from turning against those who have trusted it and have acted with its assistance. It therefore establishes the temporal and applicatory conditions for law to function. Without these the laws cannot respect taxpayers as human beings and citizens, so that law cannot be an instrument of civility in treatment and decency in action. Hence it can be said that the legal certainty principle determines the temporal and applicatory conditions for tax law to function in a humane and civilized manner.

If we combine the above considerations, we can summarize the legal certainty principle as the principle that acts as a foundation for the validity and instrumentalization of the efficacy of legal norms, requiring transparent respect for the actions of citizen taxpayers and of the pertinent argumentation, by means of state moderation.

This study has drawn several conclusions that show the functions performed by legal and tax law certainty in the legal order, functions that are unrivaled by those of other principles. To specify each and every one of them would be unjustifiably excessive. At this time it suffices to summarize some general conclusions, whose importance surpasses the mere local aspects pinpointed throughout this text.

1.1 In its preponderant normative meaning, legal certainty is a principle norm, because it establishes a state of affairs that ought to be sought through behavior that produces effects that contribute to its gradual promotion. Its application requires comparing a norm (the legal certainty principle) with another norm (a statutory, administrative or judicial norm), and its distinctive character resides in the interposition of a norm between the higher norm and the facts. Unlike a material principle, which requires a correlation between the effects of an act and the state of affairs it aims to realize, the legal certainty principle requires a correlation between the effects of a norm and the state of affairs whose realization it establishes.

1.2 The prevalent normative meaning of legal certainty, highlighted herein, does not exclude the existence of other normative dimensions that perform various different efficacy-related functions. Thus besides being a legal principle, legal certainty can be manifested as a principle legislatively concretized in a rule, such as the rule that bans tax retroactivity, or the rule that protects acquired rights, completed legal acts and res iudicata; a principle concretized jurisprudentially in a rule, examples of which are the individual norms issued by court decisions pertaining to the protection of legitimate trust or the inviolability of individual situations due to the passage of an extended period of time; a metanorm for the interpretation and application of other norms, such as the rule that bans the application of analogy in tax law; or a subjective right resulting from reflexive application of the legal certainty principle itself, such as the individual rights guaranteed by the judiciary based on the so-called trust protection principle.

2.1 The content of the legal certainty principle cannot be analyzed save from an analytical perspective whereby the ambiguity and vagueness of its constitutive elements can be reduced and its various aspects indicated: substantive (legal certainty in what sense?), objective (legal certainty of what?), subjective (legal certainty for whom, in whose view and by whom?), temporal (legal certainty when?), quantitative (legal certainty in what measure?) and justificatory (legal certainty for what and why?). Each of these elements in turn raises a number of questions internally, and in aggregate the answers to these questions will ultimately show which meanings of legal certainty are possible.

2.2 This analytical perspective is indispensable in tax law, both in order to define the content of legal certainty within this normative field and in order to ensure that other, divergent purposes are not pursued in its name, such as the maintenance of revenue from the collection of taxes, used for example in the control of constitutionality as a reason to uphold the past effects of a tax statute declared unconstitutional by the Supreme Court.

3.1 Among the possible meanings that can be assigned to legal certainty as a principle norm, the legal order will indicate which of the analytically discernible meanings should be chosen to make up its structuring aspects, by examining its superstructure (the whole) and its constitutional structure (the parts).

3.2 Examination of the legal order is indispensable not only to show that legal certainty does not have the same content in every country, but also to show that in the field of tax law it has equally different density, in that it is more protective of taxpayers, guaranteeing respect for their fundamental rights, as clearly exemplified by the constitutional norms that “limit the power to tax” or establish “guarantees for taxpayers”.

4.1 Analysis of the constitutional superstructure shows that the Brazilian Constitution not only protects legal certainty, but also embodies legal certainty itself: It establishes more rules than principles, and insists on stipulating the competent authorities, the laws to be passed, the content to be implemented, the procedures to be followed, and the subjects to be covered, favoring through such prescriptions the ideals of normative knowability, reliability and calculability.

4.2 These ideals are even more clearly embodied with still greater protectivity in the National Tax System, which encompasses a set of norms designed to specify which taxes can be created (direct taxes, service taxes, improvement contributions, compulsory loans, social contributions, intervention contributions, and dues paid to professional bodies), how they can be levied (by statute, with certain taxes specified in the Constitution requiring definition of key elements in supplementary laws), when they can be enforced (from the following fiscal year or 90 days after the law creating them is passed, and always applied to events that occur after that), and to what extent they can restrict the fundamental rights of taxpayers (neither more nor less than necessary for their efficacy).

5.1 Our examination of the structure of the Constitution shows that legal certainty is an unequivocal positive principle of the Constitution, which protects it directly by “ensuring certainty” as a “right” and as a “value”, or by regulating its reflexive efficacy through the protection of acquired rights, completed legal acts and res iudicata, and indirectly when it provides for certain types of behavior that promote the ideals of calculability and reliability, a key part of legal certainty, and establishes broad, restricted or specific ideals whose realization presupposes or implies the existence of the same ideals; it shows that the Constitution not only guarantees legal certainty but also protects it in many of its dimensions, i.e., as certainty of law, before law, of rights and as a right; it shows that the Constitution not only protects legal certainty in all of its manifestations but does so by assigning high priority to legal certainty in the constitutional order, through the way legal certainty is assured by the totality of the constitutional order and by its parts, through the insistence with which the Constitution protects legal certainty, through the independence of its foundations, and through the reciprocal efficacy of these same foundations; finally, it shows that the Constitution protects legal certainty in favor of citizens and against the state.

5.2 Our analysis of the structure of the tax system shows clearly that tax norms – principles and rules – insistently protect the ideals that make up legal certainty. In defining the concept of tax, types of tax, tax competence rules, limitations on the power to tax and the sources of tax law, and in establishing certain principles, such as equality and fiscal transparency, the Constitution defines what can and what cannot be taxed, as well as how taxation is to be configured, thus favoring the ideal of knowability of tax law through the accessibility, breadth and clarity of its norms; in banning tax retroactivity and guaranteeing acquired rights, completed legal acts and res iudicata, the Constitution prescribes when taxation may produce effects, thus establishing the ideal of reliability of tax law through the permanence of the legal order and the inviolability of certain predetermined situations; in establishing the tax anteriority rule, the equality principle in tax matters and the procedural principles that apply to tax procedures and lawsuits, including due process of law and reasonable duration of proceedings, the Constitution allows taxpayers to anticipate and measure the consequences that will be assigned to their acts and to the acts of the administration, thus favoring the ideal of calculability of tax law through the anteriority and continuity of the legal order.

6.1 This protective connotation of legal certainty, although not necessarily individualistic, is given by the form and content of its foundations: by the form, because its foundations embody individual guarantees and rights with a defensive meaning, administrative principles that restrict the arbitrary exercise of power, and structuring principles that also limit power and protect individual rights; by the content, because the foundations are based on expected types of behavior or ideals, thus implying or presuming certainty in favor of the rights, freedoms and dignity of the citizen taxpayers.

6.2 In tax law, this connotation of protection for legal certainty is also reinforced by the form and content of the norms in the tax system: by the form because the constitutional norms use the expressions “limitation of the power to tax” and “taxpayer guarantees” in a sense that clearly ensures the individual rights of taxpayers against the power to tax; by the content thanks to the ideals of normative knowability, reliability and calculability that tax norms protect, either directly or indirectly.

7.1 The word segurança in the Constitution refers to legal certainty because when article 1 institutes a democratic state based on the rule of law with the aim of “assuring certainty as a value,” it refers to a social objective that transcends the merely psychological or physical dimension; because when article 5 assures the “right to certainty” alongside the right to freedom, equality and property, which are qualified as objective social values and not merely individual psychological states, it implies the protection of certainty in parallel to the assurance of these other values; because among the fundamental rights listed in the indents to article 5 several relate to physical and individual security (protection of the home and guaranteed habeas corpus against abusive restrictions of freedom), or to specific forms of freedom (of thought, opinion and belief, intellectual, artistic and scientific inquiry, of communication and expression, and of association for lawful purposes), presupposing a broader scope for the provision in the article’s head paragraph.

7.2 In the field of tax law, the legal character of certainty is even more crystal-clear, especially because in the tax system the Constitution emphasizes aspects linked to the quality of law (via the competence rules and the rules of statutory legality, anteriority and irretroactivity), and to forms of protection for rights (via taxpayer guarantees and procedural principles applicable to tax affairs, such as due process of law and reasonable duration of proceedings, not to mention other more specific guarantees such as the writ of mandamus).

8.1 The substantive aspect of legal certainty, as far as the term “certainty” is concerned, denotes a state of knowability, reliability and calculability: knowability, rather than determinacy, in light of the congenital indeterminacy of language and the dependency of law on criteria and arguments that are indispensable to the process necessary to its determination and concretization; reliability, rather than immutability, because the Constitution contains both entrenched clauses, making changes difficult but possible, and the principle of the state based on the social rule of law, which requires the state to perform a planning function and act for the general good by driving social change, especially through the distribution of wealth; calculability, rather than (absolute) predictability, because although the Constitution contains a number of rules designed to permit the anticipation of state actions, such as the legality and anteriority rules, the nature of the law, involving the use of indeterminate language that depends on argumentative processes to reconstruct meanings, prevents its enunciations from being semantically univocal.

8.2 These ideal states of normative knowability, reliability and calculability are also visible in the field of tax law: knowability, rather than determinacy, for the same reasons relating to language, but also because of the very reality taxes are designed to regulate, in that some taxes, duties and charges, such as contributions for intervention in the economic domain (CIDE), and even some duties, cannot be concretized with the same degree of determinacy as traditional direct taxes; reliability, rather than immutability, because by establishing tax irretroactivity and other guarantees in the tax subsystem, including protection for acquired rights, completed legal acts and res iudicata, the tax system presupposes the possibility of changes to the legal order, provided certain limits and transition rules are observed; calculability, rather than (absolute) predictability, because precisely by limiting change the tax system presupposes that changes will be made, on condition taxpayers are not surprised or deceived.

9.1 The indication of these ideal states, unlike the ideals of determinacy, immutability and predictability, shows that the conception of legal certainty follows a conception of law that intermediates the objectivist and argumentative conceptions: Law is neither a previously given object whose content depends exclusively on cognitive activities that reveal predetermined meanings, nor an activity whose realization derives solely from argumentative structures to be revealed only at a later stage in the decision process, but rather a composition between semantic and argumentative activities – the activities of users of law begin with the reconstruction of normative meanings through rules of argumentation, but depend for their application on hermeneutical and applicatory postulates that reveal normative and factual elements, so that legal certainty ceases to be a mere requirement of predetermination to substantiate a standard of rational and argumentative controllability.

9.2 This understanding is highly important in tax law, especially to show that in this normative field legal certainty cannot be identified with (or exhausted by) the requirement of determinacy of normative hypotheses, which legal doctrine identifies with the so-called closed typicality principle, but must instead comprise other elements linked not only to clarity and intelligibility of tax norms, but also to their uniform and non-arbitrary application in tax proceedings and cases. This novel and broader perception of legal certainty in the field of tax law does not eliminate the importance of aspects relating to the determinacy of norms (certainty of content); however, it helps combine these aspects with others that are equally important to a complete vision of tax law certainty, such as those relating to the existence, validity and efficacy of tax norms (certainty of existence, validity and efficacy), changes to tax norms over time (certainty of transition), application of tax norms through administrative proceedings and court rulings (certainty of realization), continuity of tax law regimes (rhythmic certainty), and the time taken to resolve tax litigation (certainty of definition). Only a balanced combination of all these phases permits full efficacy of tax law certainty.

10.1 As for the substantive aspect regarding the word “legal,” the Constitution points to several possible meanings, depending on the chosen perspective: certainty of law, because in establishing the legality, anteriority and irretroactivity rules it lays the foundations for law itself to be certain, by virtue of the clarity of its enunciations and the predictability of its norms, and in defining the morality and publicity principles it enshrines justification and publication as requirements for the validity of legal norms; through law, because by stipulating that Brazil is a democratic State with the aim of “assuring certainty as a value” in article 1 it establishes that law must act as an instrument to guarantee certainty; before law, because state action, which cannot be performed save through the exercise of powers defined in competence rules and through the sources and procedures defined by law, must not jeopardize rights acquired or guaranteed by individuals in accordance with law; of rights, because protection for acquired rights, completed legal acts and res iudicata in article 5, XXXVI, translates the reflexive efficacy of the legal certainty principle, oriented to a specific subject and concrete case, while assuring the exercise of certain rights; as a right, because the reflexive efficacy of the objective legal certainty principle gives rise to a specific subject’s right to certain state behavior without which knowability, reliability and calculability cannot be minimally realized; in law, because legal certainty as advocated in this book is not centered on the requirement of knowledge of totally predetermined content, but on the controllability of argumentative structures required in the reconstruction and application of factual and normative meanings.

10.2 These several meanings are also reproduced in the field of tax law, since there are norms that favor certainty of law by dealing with the quality that tax norms must have or the effects they can produce (the legality, anteriority and irretroactivity rules); norms that emphasize certainty through law by assuring taxpayers’ rights (rules that protect acquired rights, completed legal acts and res iudicata, or establish equality of tax treatment, including treatment according to economic capacity) or by assuring procedures and processes designed to protect taxpayers’ rights (rules that guarantee the right to a full defense and the adversarial principle, use of the writ of mandamus and habeas data); tax norms that focus on certainty before law by establishing jurisdictions, authorities, procedures and sources necessary to the exercise of the power to tax (competence rules, the legality, anteriority and irretroactivity rules, the rule that bans the use of taxes with confiscatory effects); tax norms that establish a certainty of rights, by being termed “guarantees”, as exemplified by the guarantees of acquired rights, completed legal acts and res iudicata, but also by defining general criteria for the configuration of taxation in accordance with manifestations relative to the taxpayer (the equal treatment and contributive capacity principles, and the rule that determines respect for the taxpayer’s fundamental rights and guarantees); tax norms that define certainty as a right to the extent that they attest to its orientation toward protecting taxpayers from the state’s exercise of its power to tax (limitations on the power to tax and individual fundamental rights). Similarly, all such meanings, when combined in a unitary perspective based in turn on a semantic-argumentative concept of law, show that tax law certainty must be sought not only in the previous and abstract content of norms, but in the very process of realization of tax law.

11.1 The objective aspect of legal certainty reveals the certainty of the legal order, because several principles, such as the rule of law and the social rule of law, are concerned with the legal order in its entirety, and not one particular manifestation of it; of a norm that is both general, given that several rules impose conditions of validity for the creation of norms, such as the rule of prohibiting tax retroactivity, and individual, given that several rules protect individual situations assured by court decision or administrative act, such as the rule that protects acquired rights, completed legal acts and res iudicata; of behavior, especially state behavior, considering that the Constitution not only establishes the morality and publicity principles but also contains a number of procedural and substantive rules that favor the knowledge and justification of state activities.

11.2 This breadth is also present in the field of tax law, given the existence of norms that protect the certainty of the order and its application, such as the legality, anteriority and irretroactivity rules, and the rules and principles pertaining to tax procedures and proceedings; of a general norm, such as the rules about the sources of tax law, especially the constitutional rule that restricts the creation of general norms to supplementary laws; of an individual norm, as exemplified by the guarantees of acquired rights and res iudicata; and of state behavior, given the principles that regulate state action, such as the principles of morality, impersonality and state transparency, fiscal transparency included.

12.1 As for the subjective aspect, the subjects that must guarantee legal certainty are the legislative, executive and judiciary: the legislative because of the Constitution’s rules governing the creation of norms, such as the legality, anteriority and irretroactivity rules, that require the legislative to institute obligations through formal statutes, and provide for events that may occur after a certain period and situations that occur only after the statutes are enacted; the executive because of the Constitution’s norms governing the uniform application of legislation, such as the equality principle, and the requirement of compliance with the rules established by the legislative, of which the legality rule is an example; the judiciary because the Constitution requires the creation of rules to be applied uniformly and itself contains a number of rules governing the justification and publicity of judicial activity.

12.2 This breadth of the subjective aspect of legal certainty is also evident in the field of tax law, since in this field too it must be assured by all three branches of government: by the legislative because the tax system contains competence rules for it, principles that formally and substantively delimit the power to tax, and the legality, anteriority and irretroactivity rules, which require that the legislative create tax obligations in a certain manner and with a certain efficacy; by the executive because the tax system contains both norms applicable to state action, especially the principles regarding public administration, and norms that indirectly bind administrative actions to statutory provisions and hence give rise to the executive efficacy of regulations and materially limit the creation of accessory obligations; by the judiciary because the tax system establishes procedural principles that are also applicable to administrative and judicial proceedings, as well as guarantees that may be used preventively or repressively to defend taxpayers, such as the writ of mandamus in tax cases.

13.1 The subjective aspect of legal certainty relating to beneficiaries protects the taxpayer, since the purpose of constitutional norms is on one hand to allow state action to be anticipated, as evidenced by the morality and publicity principles, and on the other to permit knowledge of the consequences assignable to the acts performed by taxpayers, as shown by the competence rules and the tax irretroactivity and anteriority rules.

13.2 The structure of the tax system also evidences the purpose of protecting taxpayers, particularly the competence rules and taxpayer guarantees assured inside and outside the tax subsystem, many of which are actually defined as “limitations on the power to tax.”

14.1 As for the subjective aspect in terms of the subject used as a parameter to gauge certainty, there must be legal certainty from the standpoint of the ordinary citizen, because the rule of law principle presumes that all citizens know the norms, not least as an instrument of democratic participation, and the publicity and morality principles have no specific addressee but are addressed to all citizens.

14.2 This emphasis on the taxpayer’s perspective is also clear in the field of tax law. On one hand, there are norms prohibiting that taxpayers be surprised (the annual and 90-day anteriority rules), deceived (the tax irretroactivity rule), unjustifiably discriminated (the principle of equal treatment in tax matters), excessively burdened (the prohibition of taxes with confiscatory effects) and arbitrarily favored (the rule that tax benefits can be granted only by a specific statute). On the other hand, there are norms that determine respect for taxpayers’ individual rights (the contributive capacity principle with an express reservation of respect for individual rights), establish guarantees (the rule opening the tax subsystem to other guarantees “assured to the taxpayer”) or establish rights to information (the fiscal transparency principle and the guarantee of habeas data). All such norms institute the “citizen’s viewpoint” within the field of taxation.

15.1 With regard to the subjective aspect that concerns the subjective extension sought by certainty, in order to know whether there is legal certainty for the individual, for a right of an individual, for the collectivity or for the legal order as a whole, the context has to be examined: Legal certainty can be both considered an objective principle of the legal order and reflexively applied to a specific subject.

15.2 This ambivalence of legal certainty is also found in tax matters. Legal certainty can be considered an objective principle of the legal order, as shown by the various requirements governing the validity and efficacy of tax norms in general (the tax irretroactivity, legality and anteriority rules, and the rule requiring supplementary laws to enact general norms). It can also be analyzed in terms of efficacy in guaranteeing taxpayers’ rights, as evidenced by the rules that protect individual aspects of the reflexive application of the legal certainty principle at an abstract level (the rules protecting acquired rights, completed legal acts and res iudicata).

16.1 Turning to the temporal aspect, legal certainty of the past, present and future must be pursued: of the present because the Constitution establishes rules for the creation of law so that citizens can know the norms they must obey in their current activities; of the past because the Constitution establishes norms that protect situations already safeguarded by law itself in the past, such as the guarantees of acquired rights, completed legal acts and res iudicata; of the future because the Constitution establishes norms governing the bindingness of law so that citizens know today how binding norms will be tomorrow.

16.2 Examination of legal certainty’s temporal aspect also shows, in the field of tax law, the importance of a whole and balanced analysis of the three temporal modes: the present because the tax system determines what events are taxable through tax competence and immunity rules, and what procedures are to be used to levy taxes through the legality and supplementary law reserve rules, instituting certainty of taxpayer orientation; the past because the tax system contains norms that establish when tax norms can produce effects, assuring that they can affect only events occurring after their enactment by prohibiting tax retroactivity; the future because the system establishes norms that avert surprises for taxpayers, such as the anteriority rule and norms that guide state actions, which cannot extend beyond the boundaries set, such as the principles pertaining to public administration, of which tax administration is a species.

17.1 With regard to the quantitative aspect of legal certainty, total certainty must be assured, in the sense that legal certainty must be more promoted than restricted. Because it involves not only a uniform ideal but also a multiform complex of ideals, internal reconfigurations of several of its aspects may be required. When the stability of law is guaranteed by protecting a person’s legitimate expectations, the intelligibility of law for other citizens may be jeopardized, as they will not be sure about what is permitted or forbidden by the legal order, and the bindingness of law may also be undermined because a formal principle will lose its effectiveness on a given point; when the stability of legitimate expectations is preserved, certainty of the past is protected but certainty of the future is impaired by potentially encouraging wagers that the effects of unlawful acts may be protected via the upholding of a consolidated situation.

17.2 In the field of tax law, it is particularly important to examine legal certainty in its entirety, given that many tax norms, even when enacted without all the required formalities, may produce intensive and extensive effects in the plane of the fundamental rights of taxpayers and in that of state action, as is the case when state governments grant onerous tax benefits over a long period of time without doing so by statute and interstate agreement, as required by the Constitution.

18.1 With regard to the justificatory aspect of legal certainty, it must be understood as a means to different ends: on one hand, the fundamental rights of freedom and property, because without stability and calculability of state action individuals cannot exercise the right to free self-determination of a life with dignity; on the other, state purposes, because state planning and action in the medium- and long-term presupposes permanently valid rules.

18.2 This instrumental character is even more visible in the field of tax law because the principles and rules relating to legal certainty established in the National Tax System as “guarantees” and “limitations of the power to tax” are a protection for the taxpayer, not the state. In exercising their fundamental rights of freedom and property, citizens often act under the motivation or guidance of tax norms, or are obliged to do so by tax norms on whose validity they rely, and there is no denying the extent to which tax norms stimulate economic activity in this way.

19.1 Legal certainty can be defined as a principle norm that requires the legislative, executive and judiciary to behave in ways that contribute more to the existence of a state of legal calculability and reliability based on its knowability, from the perspective of taxpayers and for their benefit, through the juridico-rational controllability of argumentative structures that reconstruct general and individual norms, as an instrument that guarantees respect for their capacity to shape the present responsibly and with dignity, and to plan the future strategically in a legally informed manner, without deceit, frustration, surprise or arbitrariness.

19.2 The concept of tax law certainty (or legal certainty in tax law) does not differ from the general concept of legal certainty, but emphasizes the mostly protective character that certainty takes on within this normative field owing to the existence of tax norms that establish a defensive perspective toward the fundamental rights of taxpayers, albeit in balance with moderate state action in exercising the power to tax.

20.1 This concept shows that the legal certainty principle has a static dimension and a dynamic dimension. The static dimension concerns the problem of knowledge of law, of knowing or communicating law, and which qualities law must have to be considered “certain” and thus act as an instrument of orientation for citizens in general and taxpayers in particular. The dynamic dimension concerns the problem of action in time and the ideals that must be guaranteed if law is to “assure” citizens of rights and thus act as an instrument of their protection.

20.2 In the field of tax law these two dimensions also manifest themselves, through norms that concern the static dimension of legal certainty, such as those that govern the content of tax norms (the legality rule) or their breadth (the rule reserving general norms to supplementary statutes), and norms governing its dynamic dimension, such as those that assure the stability of certain situations (the rule protecting acquired rights, completed legal acts and res iudicata, and the tax irretroactivity rule) or norms that protect anteriority and the continuity of the legal order (the tax anteriority rule and the principle of equal treatment in tax matters).

21.1 Knowability means a state of affairs in which citizens have to a high degree the material and intellectual capacity to understand argumentative structures that reconstruct general and individual substantive and procedural norms that are minimally effective by virtue of their accessibility, breadth, clarity, determinability and executability.

21.2 In the field of tax law there are several norms requiring knowledge of tax norms by taxpayers to guarantee “certainty of guidance” through access, breadth, clarity and determinacy: norms that directly or indirectly regulate tax predictability (rules establishing types of tax, tax competence rules, principles that institute taxation criteria, and norms that define the sources of tax law), the creation of tax obligations (the legality rule and the rule reserving specific subjects to supplementary statutes), the interpretation of tax legislation (the legality rule, which indirectly prohibits the use of analogy to create new tax obligations), the formation of tax credits (the legality rule, which indirectly requires the determination of credits based solely on statutory provision) and their extinction (the rule requiring supplementary statutes to create general norms of tax law, especially governing prescription and limitation in tax matters).

22.1 Reliability means the ideal state in which citizens can know which changes are allowed or prohibited, thus avoiding frustration of their rights. This reliability exists only if citizens can be assured today of the effects that law assured them yesterday, which in turn depends on the inviolability of past situations, the durability of the legal order, and the irretroactivity of present norms.

22.2 In the field of tax law there are numerous norms relating to the credibility of tax norms and designed to assure taxpayers of what is called “certainty of transition from past to present” through normative stability and efficacy. There are tax norms that directly or indirectly regulate the interpretation and application of tax legislation (the tax irretroactivity rule, which prohibits the modification of legal criteria in the application of legislation), the formation of tax credits (the irretroactivity rule, which indirectly determines application of the statute in force at the time the taxable event occurred and debars the application of new criteria to facts that occurred before it was enacted, and the rule requiring supplementary statutes to establish general tax norms, including tax obligations and assessments).

23.1 Calculability means the ideal state in which citizens know how and when changes can be made, so that they are not surprised. This state of calculability exists only if citizens can control today the effects law will assign tomorrow, which occurs only when citizens have to a high degree the capacity to approximately anticipate and measure a limited and fairly invariable range of criteria and argumentative structures that define consequences to be assigned, heteronomously and coercively or autonomously and spontaneously, to their own actions or those of others, or to facts that have actually occurred or might occur in future, whether or not they are in dispute, and the reasonable time frame within which the final consequence will be applied.

23.2 In the field of tax law there are several norms relating to the continuity of tax norms, whose purpose is to assure taxpayers of the so-called “certainty of transition from present to future” through the anteriority and continuity of change and the binding force of its general and individual norms. There are tax norms that regulate the object and manner of taxation, allowing taxpayers to measure the range of future taxation, that anticipate the future effects of tax laws, such as the anteriority rule, and that govern oversight of compliance with tax obligations (principles applicable to tax proceedings and cases, such as due process of law and the rules requiring justification and publication of acts and decisions).

24.1 If we combine the two dimensions of the legal certainty principle, the static and dynamic, we can see that in aggregate it seeks to guarantee an ideal state of respect for the human being, free from deceit, frustration, surprise and arbitrariness, and hence to protect a respectful transition from past to present and from present to future. In light of these elements, it must be redefined as a condition principle that assures a state of respect for the fundamental rights of the citizen taxpayer and moderation of state action through juridico-rational controllability of the argumentative structures that reconstruct general and individual norms, or simply as a principle that assures the respectability of the taxpayer as citizen.

24.2 The proposed concept of tax law certainty promotes a shift in several aspects of the discussion involving legal certainty: Instead of a concept of legal certainty that is exclusively linked to security through knowledge of prior abstract determination of legal hypotheses, that is verifiable by means of linguistic description, and in which law is the creation of only one branch of government, preceding its application as something entirely given, the concept presented is of legal certainty centered on argumentative control and observable thanks to the use of language, through knowledge of hermeneutical criteria and structures, and in which law is a product of experience and a combination of objective and subjective aspects inherent in its application. We move beyond legal certainty as a guarantee of content based on the paradigm of determinacy, to understand legal certainty as a guarantee of respect grounded in the paradigm of semantic-argumentative controllability and whose realization depends on elements, dimensions and aspects to be assessed together.

25.1 With regard to the protection of trust, verification of the existence of a basis for trust entails examining several criteria concerning elements that interact with one another, and are always linked on one hand to the fundamental rights of freedom, property and equality, and on the other hand to the principles that govern state activity, so that the absence of a law in itself cannot override the production of effects by the benefits, and the normative acts that grant them must be analyzed in terms of permanence, individuality, onerousness, efficacy over time, realization of purposes, appearance of legitimacy, dependency of the addressees, and behavioral conduciveness.

25.2 In the field of tax law, application of the so-called trust protection principle is enormously relevant to the granting of tax benefits that may not observe the formalities required by the Constitution, as is the case of benefits granted without a specific statute and without an interstate agreement. In these cases, not only the formal aspect but also other elements must be analyzed, such as the degrees of permanence, individuality, onerousness, efficacy over time, realization of purposes, appearance of legitimacy, dependency of the addressees and behavioral conduciveness linked to the tax benefit concerned. Only a balanced and complete observation of all such elements can focus simultaneously on state action and the exercise of fundamental rights in the plane of tax law, so that those who have legitimately relied on the validity of the normative acts concerned are neither deceived nor surprised.

26.1 Whether the exercise of freedom is an indispensable requisite for trust protection is resolved first by checking what kind of stability is intended: stability of the legal order as a whole, based on the objective face of the legal certainty principle, which requires normative durability (reliability through permanence) and a stable, moderate and consistent normative development (calculability through continuity), or relative to a concrete situation, based on the reflexive application of the legal certainty principle, which bans unjustified restrictions on the past exercise of legally oriented freedom (reliability through trust protection); and second, therefore, by verifying whether the intended stability is or is not grounded in individual fundamental rights.

26.2 In tax law these two kinds of stability can be sought and protected. In certain situations upholding a tax benefit, especially for the past, after considering the indirect effects produced by the tax benefit and examining the affected good-faith third parties, contributes crucially to the credibility of the legal order. In other situations, regardless of these elements taxpayers may have performed acts of disposal of their fundamental rights of freedom and property so that upholding the benefit is a condition for taxpayers to rely on the legal order and a requirement for state action not to create surprise or deceit.

27.1 The greater the resulting onerousness, the longer lasting the efficacy of the basis for trust, and the harder it is to reverse the effects produced, the more intensely the fundamental rights of property and freedom will be restricted and hence the greater will be the duty to protect trust and the more justifications will be required for not doing so.

27.2 Consideration of these elements is essential to transcend the merely formal analysis of tax benefits focusing exclusively on the formal regularity of state action, by investigating both state action and its moderation, and the taxpayer’s exercise of fundamental rights and its intensity, which often collaborates in the promotion of public purposes.

28.1 All elements of the trust protection principle (basis for trust, trust, exercise of trust, and frustration of trust) have to be present, but low intensity in one should be offset by high intensity in another, so that on average the minimal density of its presuppositions can be affirmed.

28.2 This combined and balanced assessment of all elements of the trust protection principle shifts the analysis of the effects of tax benefits from the abstract to the concrete level, so as to permit an analysis of both state action and the exercise of fundamental rights.

29.1 With regard to the prohibition of retroactivity, in the case of an act consummated in the past (an acquired right, completed legal act, res iudicata and/or a past taxable event), retroactivity is prohibited by the rules, so that mere horizontal weighing of any kind is precluded; when a fact foreseen in the norm has begun, but has not yet been completed or consummated according to the legislation, and therefore cannot be protected by the rules of irretroactivity, it will be necessary to verify the existence of the presuppositions that configure the trust protection principle, so that improper retroactivity or retroactive reference to past de facto situations is averted, and a state of trust protection can be held to exist when all of its elements are provided for in larger measure, which is the case when low intensity of one element is offset by high intensity of others.

29.2 The sole purpose of the “tax irretroactivity ruled linked to the taxable event” is to preclude the horizontal weighing of situations covered by its incidence hypothesis (taxable events whose occurrence is linked to acts of disposal by taxpayers), without precluding protection of taxpayers outside it: When the acts have not been consummated in accordance with the statutory provisions, there is protection relative to taxable events, in accordance with article 150, III, “a”, and otherwise in accordance with article 5, XXXVI, so that even where no act or fact has been completed in the past, there can be acts of disposal by taxpayers and state conduct that justify setting aside the retrospective effects of legislation.

30.1 The problem of retroactivity ceases to be a problem of relationships between norms over time (intertemporal law) and becomes a problem of non-arbitrary restriction of fundamental rights and of fair and justified state action: A norm is retroactive not only if it affects a completed taxable event, but also if it affects a disposal that was consummated because of the incidence hypothesis in force at the time, so that it can no longer be reversed by a reaction of the taxpayer.

30.2 This new way of analyzing tax retroactivity means that the key is no longer whether events have occurred, but whether fundamental rights have been exercised and to what extent. The term continuing taxable events, considered superseded by the consideration of specific events according to normative hypotheses, regains importance and justifies reexamination from the perspective of fundamental rights.

31.1 The modification of administrative acts does not depend on their invalidity, but on the intensity of the taxpayer’s action based on trust in them and on the intensity of the restriction that such modification will cause. Administrative actions cannot be ruled null and void merely because they are formally unlawful.

31.2 In the field of tax law, administrative change can no longer be seen as resulting merely from an analysis of convenience and opportunity by the administration. Instead it must be the result of combined action by the administration and the taxpayer, so that when there is legitimate trust only revocation for the future together with transition rules will be capable of harmonizing public and private interests.

32.1 The examination of jurisprudential change and its effects depends on its definition. It can be defined as a direct conflict between two valid, efficacious and definitive decisions on the same subject, so that jurisprudential change is not to be confused with innovation or divergence. However, change is not enough to cause protection. Protection should be guaranteed only when there are acts of disposal of fundamental rights based on a modified decision that could be considered final within the jurisdiction of the adjudicating body.

32.2 In the field of tax law, jurisprudential change assumes particular importance when taxpayers perform acts of disposal of fundamental rights based on a court decision that is changed later on. In this case it is necessary to verify the presence of a basis for trust, characterized by bindingness and a claim to permanence, and of legitimate trust on the part of the taxpayer, as well as whether acts of disposals of fundamental rights have been oriented by the modified decision and whether trust has been intensely frustrated by the modifying decision. In the presence of these elements, only the concrete case will indicate whether the prospective efficacy of the modifying decision or the transition rules will harmonize the duty to assure permanence with the need for change in the legal order.

33.1 Modulation of effects is allowed in judicial review but restricted, depending on certain preconditions (exceptionality of the case under adjudication and absence of clear unconstitutionality of the disputed act), purposes (restoration of the “state of constitutionality,” direct protection of objective legal certainty and indirect protection of fundamental rights, avoidance of a “grave” threat to legal uncertainty) and procedures (guaranteed adversarial debate on modulation, preservation of retroactive efficacy for the precursor case, parallel cases and those not affected by statutes of limitations, and secure modulation based on legal certainty).

33.2 Modulation of effects to uphold past effects of tax statutes declared unconstitutional cannot usually be based on the legal certainty principle, since in the field of tax law this principle protects taxpayers from the state. A declaration of unconstitutionality of a tax statute, unlike other statutes that guarantee fundamental rights, immediately restores the violated state of constitutionality, and there is no reason not to rule it invalid. Moreover, upholding the effects of an unconstitutional tax statute eliminates the resistance embodied in fundamental rights and the minimal efficacy of the principle of universality of jurisdiction.

34.1 Legal certainty as embodied in the Constitution not only cannot be used by the state to support the restriction of the fundamental rights of freedom, but also cannot justify the upholding of effects where the creation of tax obligations is concerned, because doing so restricts rather than promotes legal certainty: Upholding the past effects of an unconstitutional norm with the intention of protecting legal certainty in the past restricts legal certainty in the future to an even greater extent by encouraging new unconstitutional norms, which in turn stimulates restriction of the efficacy and calculability of law.

34.2 In the field of tax law, upholding the past effects of unconstitutional tax statutes encourages future enactment of unconstitutional statutes, given the inevitable financial impact of any tax norm: If the financial impact of a declaration of unconstitutionality with ex tunc effects is the justification for modulating the effects of the decision, the greater the impact the more likely are the effects of the statute to be upheld. Thus the more restrictive the tax statute, the greater its financial impact; and the greater its impact, the more likely the statute is to be considered constitutional. The result of this perverse line of thinking is that the “more unconstitutional” a tax statute, the more likely it is to be considered constitutional. This understanding is manifestly opposed to the legal certainty principle, to the most elementary requirements of the rule of law, and indeed to rationality itself.

35.1 Legal certainty presupposes the conditions for realization of the norms on which citizens rely when performing acts that dispose of their fundamental rights. This “certainty of realization” depends both on the fundamental right to judicial protection and on institutional conditions without which this protection cannot be effective. The principle of due process of law, as a logical procedural consequence of the efficacy of fundamental rights, establishes the conditions without which citizens cannot defend themselves from state action that is restrictive of their rights.

35.2 In the field of tax law, “certainty of realization” presupposes the existence of effective taxpayer defense mechanisms against any kind of restriction of their fundamental rights, in terms of enforcement procedures and administrative or judicial proceedings. Without the guarantees inherent in due process of law (an impartial natural judge, notification and publication, the adversarial principle, full defense, inadmissibility of unlawful evidence, express, rational and motivated justification of decisions, possibility of appeals), the legal certainty principle cannot be made effective in the field of tax law. And without the requisite institutional conditions, i.e. independence of the judiciary, access to the judiciary and the judiciary’s duty to decide any case presented to it, taxpayers cannot be defended against the power to tax.

36.1 Legal certainty requires the certainty of transition from present to future through anteriority, continuity, and normative bindingness. Only through these guarantees can the freedom exercised by citizens in the present be assured in the future without surprises or deceit.

36.2 In the field of tax law, these requirements translate especially into a need for moderation in changing tax norms. Changes in any legal regime can be considered compatible with the fundamental rights of taxpayers only when there are transition rules and equity clauses capable of harmonizing the need for change with the duty to respect the past actions of taxpayers.

37.1 Legal certainty also requires future state action to be coherent with past state action, unless there is a sound justification for abandoning the rules previously applied, and always by enacting transition rules and equity clauses.

37.2 In the field of tax law, the requirement of normative continuity via the prohibition of arbitrariness prevents the state from adopting the guiding principles of a given tax law regime only to abandon them without any justification, on pain of violating the legal certainty principle.

38.1 The legal efficacy of the legal certainty principle involves its normative function, in the sense of how it produces effects on other norms or human behavior, and its normative force, in the sense of how it is positioned with regard to other norms. The normative function of the legal certainty principle is relative since the configuration of its normative quality and its several efficacy functions depends on the perspective from which it is analyzed.

38.2 These efficacy functions are repeated in the field of tax law, since the normative force of certainty and its efficacy functions also need to be assessed in this normative sector. Given the foundational character of the legal certainty principle for the validity of tax norms, its normative force can never be completely overridden.

39.1 If the legal certainty principle is investigated in terms of its relationship with principles that impose the realization of an even broader state of affairs, it takes on the role of subprinciple and plays a definitional efficacy function with regard to such an ideal. In this relationship and from this perspective, it assumes a position of analytical inferiority, embodying “bottom up” interpretation. This is the case with the relationship between the legal certainty principle and the rule of law principle.

39.2 In tax matters, the relationship between the legal certainty principle and the rule of law principle is fundamental, especially to avoid interpretations that ultimately uphold unlawful acts without the presence of other elements that can justify such upholding.

40.1 If the legal certainty principle is examined in its connection with principles that impose the realization of more limited ideals, it assumes the position of a superprinciple and performs different functions with regard to these ideals: an interpretative efficacy function, when it acts as a parameter for the interpretation of subprinciples; a blocking efficacy function, when it acts to prevent the concrete application of one of the subprinciples that prove locally incompatible with the broader state of affairs; an integrational efficacy function, when it acts as an instrument to fill the void created by local rebuttal of a subprinciple.

40.2 This is the case, in the field of tax law, with the relationship between the legal certainty principle and the principles of statutory legality (as an ideal of predictability of state action), irretroactivity (as an ideal of legal regulation for future cases) and trust protection (as an ideal of protection for acts of disposal causally linked to previous state action): The legal certainty principle, as superprinciple, acts as an interpretative parameter to redefine what is more narrowly determined by its subprinciples, or as a norm capable of blocking the application of a subprinciple and subsequently filling the vacuum thereby created.

41.1 If the legal certainty principle is seen in terms of its direct action, with no interference by any norms, be they principles or rules, it acts as a principle and directly performs an integrational efficacy function, filling the originary void created by the lack of rules or principles that specifically regulate the situation.

41.2 In tax matters, the integrational efficacy function evidences the unnecessariness of infraconstitutional rules to establish requisites indispensable to normative knowability, reliability and calculability, given that the direct efficacy of the legal certainty principle suffices to assure the conditions for validity and efficacy of general and individual tax norms.

42.1 If legal certainty is examined in its relationship with other norms, i.e. in terms of its indirect efficacy, it may play the role of subprinciple if analyzed from an angle that examines its relationship with a norm that establishes a broader ideal to be reached, or it may play the role of superprinciple if analyzed from a position that involves its connection with norms that determine more limited ideals.

42.2 In the field of tax law, the legal certainty principle acts both as an element that concretizes the rule of law principle, especially to quash unlawful acts that do not respect the separation of powers, the normative hierarchy, or the clarity and prior knowledge of norms, and as an element that defines other more restricted ideals, especially those concerning statutory legality and irretroactivity in the application of tax norms.

43.1 The Constitution establishes legal certainty rules in various sectors. For example, it protects res iudicata, acquired rights and completed legal acts, and it prohibits the retroactivity of tax statutes relative to the taxable event. In these cases, instead of being an element to be weighed, as a principle legal certainty is constitutionally concretized through rules that as such cannot be subjected to mere horizontal weighing.

43.2 This regulation of legal certainty is especially relevant in tax law, where its purpose is to avoid mere horizontal weighing to set aside res iudicata in tax matters or to justify the use of illicit evidence in tax proceedings. In certain areas the regulation of legal certainty reinforces the efficacy of taxpayer guarantees that cannot be overridden even by the consideration of state tax collection or prosecution purposes.

44.1 The objective efficacy of the legal certainty principle can experience a “right to certainty”, from a concrete and subjective perspective, that is nothing more than the legal certainty principle in its reflexive efficacy.

44.2 In the field of tax law, the right to legal certainty does not permit a demand for general tax policies, which are reserved to the jurisdiction of the legislative and executive, but does at least permit a demand for specific manifestations that guarantee it in some situations, mostly by avoiding surprise and deceit in state action.

45.1 Since the legal certainty principle requires the combined realization of several states of affairs, some of which are intermediate, some ultimate, and which do not necessarily coincide, it may be that in a given case to be decided by a court legal certainty conflicts with itself, as it were, in the sense that the promotion of one state of affairs causes the restriction of another state of affairs that is concretely and directly opposite. The solution is to balance these ideal states so that the search for legal certainty causes an overall increase in certainty, i.e., so that the use of the legal certainty principle as a foundational justification for a given decision leads to a greater average realization of the ideal states of which it is made up of than would otherwise be the case.

45.2 In the field of tax law, the use of the legal certainty principle must never entail more restriction than the opposite, considering not only past, present and future, but also its static and dynamic aspects in aggregate. Legal certainty is either whole or it is not legal certainty.

46.1 The principle of legal certainty understood as a norm that establishes the ideals of knowability, reliability and calculability of law can never be discarded. What may happen is that in some cases one element of one of its ideals in one of its dimensions may be differently calibrated by virtue of its relationship with ideals in other dimensions, but legal certainty can never be completely set aside in the unity of its ideals. All that may happen is the application of one element to a smaller degree to favor the application of one or more other elements to a greater degree.

46.2 Although legal certainty is a principle, it is a norm that establishes the pursuit of an ideal state of affairs without specifying the means necessary to its realization, and as such it lacks the prima facie efficacy some principles have, as norms that may be temporarily inapplicable (prima facie efficacy as defeasible normative force), that can be overridden in concrete cases (prima facie efficacy as overridable normative force), or that can be limited in their unity (prima facie efficacy as limitable normative force).

47.1 The legal certainty principle, therefore, is a norm with sui generis efficacy unlike that of all other principles, a sort of “condition norm” or “structure norm”, in the sense that unless it is minimally effective no other norms can have minimal efficacy. It is an “intermediation principle”, establishing functional conditions for the principles and rules that make up the legal order.

47.2 In the field of tax law, understanding legal certainty as a principle that conditions the validity of tax norms and instrumentalizes their efficacy means that it cannot be completely set aside, even on pretext of realizing public purposes relating to tax collection or the enforcement of tax obligations, whether principal or accessory.

48.1. The tax law certainty principle assumes a special character because there are specific and emphatic norms in the National Tax System that serve as instruments to assure the intelligibility of law through the determinability of incidence hypotheses (the legality rule and the system of competence rules); the reliability of law through stability over time (the rule restricting the regulation of prescription and limitation to supplementary laws), periods of validity (the rule prohibiting retroactivity), and procedure (rules that expressly apply rights and guarantees not in the tax subsystem, such as protection for acquired rights, completed legal acts and res iudicata); and the calculability of law through non-surprise (the anteriority rule).

48.2 These specific rules endow the ideals whose realization is determined by the legal certainty principle with an aspect of resistance or protection. This character is revealed for instance in the redefinition of the irretroactivity principle and rediscussion of the use of modulation in the field of tax law.

49.1 The juridical goods restricted by concretization of the tax obligation relationship, usually in respect of freedom, property and equality, have an even more prominent claim to protection because even more weight should be given to the protective character of the legal certainty principle depending on the object, intensity and purpose of the limitations placed on fundamental rights, especially where acts have been performed to dispose of the fundamental rights of freedom and property, and disrespect for such acts treats the citizen taxpayer as a mere object.

49.2 Therefore the legal certainty principle’s character of resistance or protection in tax law is not uniform. It is greater in abstract given the existence of abstract norms that assign a generally protective character; concretely, however, it must be all the greater, the more suddenly and drastically the fundamental rights of freedom, property, equality and dignity of the citizen taxpayer are restricted.

50.1 The legal certainty principle is a condition principle that on one hand assures a state of respect for the fundamental rights of the citizen taxpayer and on the other hand assures an ideal of moderation of state action. Its definition as a principle that preserves the respectability of the action and argumentation of taxpayers as rational citizens causes an extraordinary change in the very analysis of tax law: The validity, enforcement and efficacy of tax norms can no longer be analyzed solely from the viewpoint of their formal structure, semantic reach or intertemporal relations; instead, these elements must be investigated from a perspective that combines the mode, rhythm and intensity of the exercise of fundamental rights in a balanced manner with the mode, rhythm and intensity of state action.

50.2 This understanding of the legal certainty principle as a principle that, while serving as a foundation for the validity of tax norms and instrumentalizing their efficacy, not only limits and directs state action, but also guarantees and respects the fundamental rights of taxpayers and the corresponding argumentation, enabling tax law itself to move away from being focused on the exercise of power by the state to being above all juridically foundational.