Chaza"l set forward a regulation that "dina demalchuta dina," the law of the land is the law (Bava B'atra 54b).
International law is a set of near-universally recognised modes of conduct between states.
Is International law binding upon a Jewish-led state where it does not cause Jews to violate a negative mitzvah?
Example: A signatory to the Geneva Convention is legally required to adhere to the precepts therein. If a nation violates this, it is in breach of international law, as it has affirmed the binding status of such a statute within International Law.