If I understand correctly (I think this was in R' Aaron Lichtenstein's book on the Seven Noahide Laws), halacha recognizes a marriage between a non-Jewish man and woman if they've gone through whatever society recognizes as marriage. (Correct me please if I'm getting that wrong.)
So certainly if they were married by a justice of the peace or the like, and the state recognizes their marriage; but what about common-law marriage? Or what if their officiant wasn't actually ordained? Or didn't register as an officiant, as is required in some states?
(I'm not trying to raise any political controversies with this question; I'm just curious.)