R. Baxter, R. Keywords: International customary law | Public international law | Law of treaties | Mots clefs: Droit coutumier international | Droit international public | Droit des traités | ABSTRACT The objective that R. Baxter assigns to his course is to describe how the treaties, whether bilateral or multilateral, serve as evidence of the state of customary international law. First, he examines multilateral treaties as declaratory of customary international law, multilateral treaties as constitutive of customary internati…