But even if they decide to strike down DOMA, there could be a way to finesse the issue. The justices could rule that on federalist grounds, the federal government doesn’t have the ability to interfere with state laws regarding gay marriage.
The overarching signal would be that the court isn’t going to interfere if states want to define marriage as between a man and a woman, but it won’t allow the federal government to define it as such at the federal level, thus undermining those states that have chosen to recognize same-sex marriage.
And as long as the Supreme Court doesn’t overturn a separate provision of DOMA, states that have defined marriage as between a man and a woman won’t have to recognize out-of-state gay marriages.
This approach could be seen as a way of preventing another outcome like Roe v. Wade, in which the Supreme Court created a constitutional right to abortion and short-circuited states’ ability to craft their own abortion laws.