In this chapter, illegal logging is discussed at length, because of its major impact on sustainability and its much greater negative impact on the forest ecosystem than the Low Impact Logging practiced by most responsible operators. Various studies on illegal logging are reviewed. The impact of cross-border illegal trade-in logs is also discussed and its impact on the displacement of both forest degradation and carbon dioxide emissions to other countries is highlighted in relation to the veracity of claims to be carbon neutral or managing forest sustainability. The most important measure to eliminate illegal logging is to assess the true sustainable level of production and strenuously limit the wood processing capacity to that level. If processing capacity exceeds the sustainable supply, it will be met with illegal logs.