This is not really a response to you, but more of a semi-related question to you that I'm asking since you're much more of a legal mind than I.
Doesn't the Constitution require that marriages from one state be recognized by all the others? Shouldn't it then be the Supreme Court's responsibility to ensure that gay marriages and civil unions from MA, VT, etc be recognized in all other states?
Even as a matter of contemporary jurisprudence, the Constitution does not require that. I previously addressed this (surprisingly popular) legend in
an earlier post. I think it adequately answers your question. Accord Patrick J. Borchers,
The Essential Irrelevance of the Full Faith and Credit Clause to the Same-Sex Marriage Debate,
38 Creighton L. Rev. 353 (2005).
The original meaning of the clause is even more minimalist: The evidence indicates that the first sentence was a
purely evidentiary command. For a lengthy analysis of the historical materials, see Ralph U. Whitten,
The Original Understanding of the Full Faith and Credit Clause and the Defense of Marriage Act, 32 Creighton L. Rev. 255 (1998).