Gay marriage and Ex Post Facto Clause:

I sometimes get from students this questions about the Massachusetts gay marriage case: If Massachusetts passes a state constitutional amendment banning gay marriages, and retroactively canceling all marriages created under the Massachusetts Supreme Judicial Court's Goodridge decision, would that violate the Ex Post Facto Clause? The answer is "no." Though the Ex Post Facto Clause restricts state as well as federal decisions -- it's one of the few federal constitutional rights that bound the states even before the Civil War Amendments -- it has consistently been interpreted as barring only retroactive criminal laws. See Calder v. Bull, 3 U.S. 386 (1798). Justice Thomas suggested in his concurrence in Eastern Enterprises v. Apfel, 524 U.S. 498 (1998) that Calder might be mistaken, but it's a pretty firmly entrenched precedent, and I doubt that courts will reverse it.

What about the Contracts Clause, which bars states from impairing the obligation of contracts? Say that the Massachusetts voters cancel existing gay marriages, and don't substitute civil unions for them, thus essentially abrogating the existing marriage contracts. Would this violate the Contracts Clause? I suspect the answer is still "no"; the Contracts Clause has generally not been seen as applying to marriage contracts, which, I take it, is why states have been allowed to relax their divorce laws. See, e.g., Adams v. Palmer, 51 Me. 480 (1863); White v. White, 4 How.Pr. 102 (N.Y. Sup. 1849). (If a state used to forbid divorces, or allow them only in rare circumstances, it was essentially treating the marriage contract as very strongly binding; the enactment of a permissive marriage law would thus diminish the legal force of the marriage contract.) But if anyone has more specific legal authority for me on this, I'd love to see it and cite it.