Despite the critical importance of applicable law in international arbitration, the concept remains misunderstood and often ignored. In the field of international investment law, whether the arbitration proceedings arise from an investment treaty or from a contract, the cornerstone principle of party autonomy applies when it comes to the choice of applicable law, as provided, for example, in article 42 of the ICSID Convention. Even that principle, however, is subject to debate, for example with respect to whether initiating arbitration proceedings under an investment treaty amounts to an implicit choice of applicable law. In an attempt to clarify the notion of applicable law, this contribution first distinguishes the rules of decision, i.e. the law applicable to the specific claims submitted by an investor against a state, from incidentally applicable law, i.e. the other laws which may be relevant for the resolution of the dispute but that do not form a basis for the decision on the merits. In a second part, this contribution analyses several questions arising from the application of choice-of-law provisions in practice, with an emphasis on article 42 of the ICSID Convention. Finally, the consequences of erring in the application of the correct applicable law are examined.

This chapter focuses specifically on the Council’s contribution to the international law on the use of force (the jus ad bellum), an area of international law that is central to the Security Council’s role in the maintenance of international peace and security and the collective security system of the United Nations. The chapter addresses, first, the general state of the rules of international law on the use of force (the jus ad bellum). It then outlines the rules themselves. This is followed by sections relating directly to the Security Council: the prohibition of the use of force; the use of force by or authorized by the Council; the Council and the right of self-defence; and the Council and ‘humanitarian intervention’ and ‘responsibility to protect’.