Introduction

There is a variety of ways in which conflicts between treaties and EU law might occur. The most obvious perhaps, and at any rate the only one which the EC Treaty makes provision for, is that obligations under EC law may come into conflict with commitments entered into by the EC's member states before the creation of the EC or, alternatively, before the date they acceded to the EC. This has found regulation in article 307 TEC, which will be discussed extensively in the remainder of this chapter.

Additionally, however, other scenarios are also possible, and in fact do occur. One is where commitments under EC law come into conflict with later commitments entered into by individual member states with third parties, either because those individual member states wittingly ignored Community law (though this is rare, perhaps non-existent) or because of the continuous development of Community law: what may still be legally possible on Monday may turn out to be prohibited on Tuesday. Alternatively, as will be discussed in Chapter 8 in particular, in many cases it is not exactly clear from the outset what Community law still leaves to its member states, and what the Community institutions can lawfully claim as falling within their proper competences.

A third category, somewhat special if technically falling either under anterior or posterior treaties, relates to two treaties that can boast some claim to supremacy: the UN Charter prevails, on its own terms, over commitments under other treaties, and the European Convention on Human Rights, while lacking a supremacy clause, has been described, by its own monitoring court, as being of constitutional character.