Commission of the European Economic Community v. Grand Duchy of Luxembourg and Kingdom of Belgium 90/63, 91/63

Application concerning the introduction by the defendants of a special duty leviable upon the issue of import licences for certain milk products

The defendants… in their view, since international law allows a party, injured by the failure of another party to performs its obligations, to withhold performance of its own, the Commission ha lost the right to plead infringement of the Treaty. However this relationship between the obligations of parties cannot be recognized under community law. In fact the Treaty is not limited to creating reciprocal obligations between the different natural and legal persons to whom it is applicable, but establishes a new legal order which governs the powers, rights and obligations of the said persons, as well as the necessary procedures for taking cognisance of and penalizing any breach of it. Therefore the fact that the council failed to carry out its obligations cannot relieve the defendants from carrying out theirs.