I'm editing a paper on international human rights. It keeps referring to a country as "a state party of ICESCR." At first, I thought it should be "party to," but then I came across a quote taken directly from the ICESCR, and it says, "States parties to ICESCR." So that confirms the "of vs. to" question, but it also seems to indicate that I've completely been parsing the phrase incorrectly all these years.
I thought it was states [that are] party to X, with party being an adjective. But if States parties is correct, then I have no idea what is going on. Do we have any other constructions like that in English? Is the phrase incorrect? Is there some sort of weird legalese going on?