Gay marriage can’t be entirely left to the states

President Obama may want to treat gay marriage as a state issue. But as Josh Barro notes, some of the policy questions it raises are irreducibly federal in nature:

What about gays who live in states that don’t have gay marriage? Should North Carolina be able to decide that its gay residents don’t get to file joint federal income tax returns, even if they are legally married by another state? Should gay federal workers get spousal benefits only if they work in gay marriage states? Or should the federal government treat gay couples as married no matter where they move?

There is also the issue of joint federal-state programs like Medicaid. These programs are operated by the states, but the federal government pays much of their cost and imposes certain rules about how states must operate them. Should the federal government require that states recognize gay marriages for the purposes of these programs?

And there is the immigration issue. Should gay marriages (foreign or domestic) be valid for immigration to the United States?

Some portion of marriage policy can be left up to the states. But gay marriage is also very much a federal issue requiring federal policy solutions. In the coming months, Barack Obama will need to address them, whether he wants to or not.