It’s not so much that his father was a British subject, and thus he is a British subject under *British* law, but rather that his father was *NOT* a US Citizen, that is problematic. US law, common or statute, doesn’t care what British law, especially statute law, has to say.
The point here isn't about the Constitutional term NBC, but a rather different "approach."
That being...Is a dual citizen head of state (POTUS for example), prohibited by international law (or even U.S. law) from entering into certain (all?) treaties. If that is indeed a true statement, then it may be yet another reason why Barry couldn't/shouldn't be POTUS...and perhaps another avenue for a lawsuit of a different type and potentially different issues of "standing", etc.
Barry is a dual citizen per himself. He admitted to being born "Governed" by G.B., and says he was born in HI (to be determined). Since there is no record of him renouncing that British citizenship....he is a dual citizen right now. Thus the question.