While preparing the recent post on Tom Palmer's attack on Hoppe, I see Palmer recommends the Cato article The Federal Marriage Amendment: Unnecessary, Anti-federalist, and Anti-democratic, by Dale Carpenter.I've posted before on related issues here: Gay Marriage Amendment; also Subsidiarity and San Francisco; and Re Gay Marriage. I tend to agree with most of Carpenter's points, namely that there should be no federal restriction (constitutional or otherwise) on what a given state does about same-sex marriage.
Carpenter argues that it's unlikely that same-sex in marriage would spread to other states by virtue of courts in the other states recognizing gay marriage under the "full faith and credit clause." He's probably right. And if that happened, we could always amend the Constitution then to make it clear that no state has to recognize other states' same-sex marriages.
But what I find interesting is that when it comes to gay marriage, Cato finally gets religion on the issue of federalism. This is the same Cato that has no problem with the illegal 14th amendment being ridiculously construed to permit federal courts to strike down state laws that violate the Bill of Rights. (See: 1, 2, 3; and the last 4 Gene Healy articles here.) Cato's Roger Pilon (whom I respect, especially for his rights theory--“Ordering Rights Consistently: Or What We Do and Do Not Have Rights To,” Georgia Law Review 13 (1979): 1171–96 and "A Theory of Rights: Toward Limited Government" (unpublished Ph.D. dissertation, University of Chicago, 1979)) even endorses the clearly unlibertarian Civil Rights Act of 1964 since it abolished (state) Jim Crow laws, even though that law also outlaws discrimination in the private workplace on the basis of race, color, religion, sex, or national origin.
I.e., Cato does not care too much about federalism, when it comes to the Fourteenth Amendment and using the feds to force states to "be good". Yet they trot out a federalist argument when Congress threatens to federally ban gay marriage at the state level. It seems to me that their real opposition to the Federal Marriage Amendment is not that it harms federalism, but that it would prohibit same-sex marriage. I.e., Cato is really in favor of same-sex marriage; Carpenter even admits in a footnote that "I should acknowledge here that I support same-sex marriage as a policy matter"; and Palmer also supports it (on his own site).
One other point--as I mentioned previously, I am not quite sure that the proposed marriage amendment actually outlaws gay marriage. I am not yet convinced that it does anything other than clarify that states can't be forced by courts to recognize gay marriage. It seems to me the amendment does not prohibit states from legislating in favor of gay marriage: the opening line, "Marriage in the United States shall consist only of the union of a man and a woman." does not say it's banned, and does not empower Congress or courts to strike down state same-sex marriage statutes, as far as I can tell.