Answer:
International law is a widely growing theory of law in the present time. there was't any idea of international law in old time. By the growth of the law fields and the dependencies of various states on others it became a very necessity for the mankind.
In the traditional sense of "law", international law is not a law and that's why: law is norms, established by state for people (traditional explanation). that's how it was until 1919, when first international organization, League of Nations, was created. after this, states begun creating norms for themselves too and not for people. This is what we call international law: Law for states established by themselves. It is not for people, except when they act as presidents, ministers, etc.