A 1999 ruling in San Antonio, in Littleton v. Prange, determined that marriage could be only between people with different chromosomes. The result, of course, was that lesbian couples in that jurisdiction were then allowed to wed as long as one member of the couple had a Y chromosome, which is the case with both transgendered male-to-females and people born with conditions like androgen insensitivity syndrome. This ruling made Texas, paradoxically, one of the first states in which gay marriage was legal.The author goes on to note that "male" and "female" are not simple black/white binaries, but elusive and changeable. Since the confusion is already rampant, isn't it simpler to say "an adult may marry one other unrelated adult of their choosing"? Since that is really what has happened.
A lawyer for the transgendered plaintiff in the Littleton case noted the absurdity of the country’s gender laws as they pertain to marriage: “Taking this situation to its logical conclusion, Mrs. Littleton, while in San Antonio, Tex., is a male and has a void marriage; as she travels to Houston, Tex., and enters federal property, she is female and a widow; upon traveling to Kentucky she is female and a widow; but, upon entering Ohio, she is once again male and prohibited from marriage; entering Connecticut, she is again female and may marry; if her travel takes her north to Vermont, she is male and may marry a female; if instead she travels south to New Jersey, she may marry a male.”
Similar confusion abounds over issues of under-age marriages, or marriages between first degree relatives. Even if it is illegal in state A for first cousins to marry, however, they will recognize marriages between first cousins performed in other states.
So it's all a mess, really, isn't it?
More information on transgender marriage equality here.