3. Repeal DOMA.
The Defense of Marriage Act (PDF) is a piece of bigoted nonsense that Bill Clinton should have vetoed. (Though to be fair, if he had vetoed it, you can bet the Republicans would have brought it back after 20th January 2001.)
Once DOMA is repealed, same-sex couples who are legally married must receive all federal recognition and benefits. The states which have passed legislation or constitutional amendments declaring that they don’t have to give full faith and credit to marriages or civil unions they don’t like, will have to deal direct with Article 4 of the US Constitution, which says rather definitely (and is backed by case law) that they do.
Okay, break’s over!