[A]rticles 267 and 344 TFEU must be interpreted as precluding a provision contained in an international agreement concluded between two Member States under which an investor from one of those Member States may, in the event of a dispute concerning investments in the other Member State, bring proceedings against the latter Member State before an arbitral tribunal whose jurisdiction that Member State has undertaken to accept… .

1. [I]n relation to commercial arbitration (…) the requirements of efficient arbitration proceedings justify the review of arbitral awards by the courts of the Member States being limited in scope, provided that the fundamental provisions of EU law can be examined in the course of that review and they can, if necessary, be the subject of a reference to the Court for a preliminary ruling (…).

2. [I]t must be concluded that Article 26(2)(c) ECT must be interpreted as not being applicable to disputes between a Member State and an investor of another Member State concerning an investment made by the latter in the first Member State.

Articles 267 and 344 TFEU must be interpreted as precluding a provision in an international agreement concluded between Member States, such as Article 8 of the Agreement on encouragement and reciprocal protection of investments between the Kingdom of the Netherlands and the Czech and Slovak Federative Republic, under which an investor from one of those Member States may, in the event of a dispute concerning investments in the other Member State, bring proceedings against the latter Member State before an arbitral tribunal whose jurisdiction that Member State has undertaken to accept.