When someone I like and respect makes a statement sufficiently at variance with reality, it's HARDER to respond, because I can't trot out the usual snark in good conscience and I have to play nice.
Federal law, in the form of the questionably constitutional federal "Defense of Marriage Act" passed in 1996 specifically bars the federal government and its' agencies from any recognition of same-sex marriage in any of its' actions or rulings (in the second section). In the first section, it specifically exempts states, tribes, and subordinate jurisdictions from recognizing/honoring/acknowledging any same-sex marriage or relationship if the whim doesn't strike them.
Subsequently, various states have passed sundry forms of state level DOMA - while somewhat outdated (4 yrs) this site reviews the variety of bans out there, some more vicious, some less. Florida's, for instance, is particularly vile - not only barring same-sex marriages from being performed within the state, but barring recognition of such marriages performed in any other state or foreign jurisdiction as well.
Progress is being made (Washington's "everything but the name" statute this year is one example), but thus far neither the state nor the federal DOMA variants have made it to the Supreme Court of the United States where, with luck, the good justices will batter the silly about the head and shoulders with the "full faith and credit" clause (Section 1) of the United States Constitution - which the various DOMA implementations appear to defy rather directly.
But that time hasn't come yet. Currenly, to invalidate a Massachusetts (For example) same sex marriage, all one must do is gather all the valuables (not required, but par for the course when dealing with the overwrought) and move to Florida sans partner (and STAY there) - no federal or state penalty will incur. In the same mode, if a person falls in love abroad with a person of the same sex and marries them in, say, Sweden - La Migra will not recognize the marriage and will not admit the spouse.
Then we look at Prop. 8 and its' subsequent effects. Oy.