I General observations 230 Treaty rules like any other rules must produce effects, which means that they must be applied, in the widest sense of the word. The fact is, however, that they are not always applied. Their non-application occurs in very different circumstances and with widely varying features, while an uncertain terminology only makes matters worse. This chapter will try to present an overall picture of non-application and point out some basic aspects of the problem, by considering first the causes and the effects of non-application in order to identify the different types of situation, and then to concentrate on the most important cases which will be further discussed in the subsequent sections.

1. Causes of non-application