international law vs law of nations

international law and law of nations both are nouns.

Word	Noun	Adjective	Verb	Adverb
international law	Yes	No	No	No
law of nations	Yes	No	No	No

As nouns, international law and law of nations are synonyms defined as:

international law and law of nations: the body of laws governing relations between nations

international law (noun)	law of nations (noun)
the body of laws governing relations between nations	the body of laws governing relations between nations