The law in question -- the Defense of Marriage Act, enacted in 1996 -- has two main parts: Section 3 defines marriage as a legal union between a man and a woman, while Section 2 allows states to refuse to recognize same-sex marriages performed elsewhere.

Still, even if the entire law disappeared, gay couples would still need to get married in one of the five states, or the District of Columbia, that perform same-sex marriages. But if they went back home to a state that did not recognize their union, they would still be strangers in the eyes of that state's government. The couple would need to continue to file their state income tax returns separately, for instance.

But this is where it gets tricky. There could also be some confusion about what sort of federal benefits the couple is entitled to receive if they live in a state that does not recognize their union. Why? The federal government typically looks to the states to define marriage. And though states generally honor opposite-sex marriages performed elsewhere, many states specifically ban same-sex marriage.