Federalism principles may weigh against Section 3 of the Defense of Marriage Act (DOMA), but what about Proposition 8? Reason.com has just posted an exchange between me and Ilya Shapiro of the Cato Institute on this question. Cato’s Ilya S. (not to be confused with our Ilya S.) argues that federalism has nothing to do with the constitutionality of Proposition 8, as the question is simply whether government refusal to recognize same-sex marriage violates the 14th Amendment. As readers might expect, I disagree. Family has been the province of state governments since the nation’s founding and there are judicially cognizable reasons why a state may opt not to recognize a marriage as other than a union of one man and one woman. While I support gay marriage as a policy matter, I do not think it is constitutionally compelled. I may find many of the justifications for maintaining a traditional definition of marriage unpersuasive, but I believe that when asserted by a state, they are sufficient to uphold the constitutionality of California’s policy. (Of course, if recent polling is to be believed, Proposition 8 may not remain California’s policy for long, no matter what the Supreme Court decides.) While Ilya and I disagree on this question, I suspect we’d both agree that the real policy question for libertarians should be whether the state has to be in the marriage licensing business in the first place — but that’s a question for another time.