In his last post on the subject, Nick Rosenkranz concludes that “the mere fact of a federal definition, for purposes of federal law, does not violate principles of federalism.” On this we are entirely agreed. And if all Congress sought to do with Section 3 of DOMA was to define the semantic meaning of a word, there would be no problem. But that’s not all Congress sought to do. Further this is not a case in which we (or anyone else) is asking the Court to pour through legislative history to divine Congressional intent, as the true purpose of DOMA has never been contested.
The ultimate question in the DOMA litigation is whether Congress has a legitimate federal interest in having a particular definition of marriage that supports the traditional form, and whether this interest is sufficient to justify the differential treatment (and disregard of marriages recognized under state law) that DOMA produces. One might have a definition so that we can know what the words mean in federal statutes, and yet still not be able to defend them with the same interests that a state might assert (as I explained here). In order to strike down DOMA, the Court need not conclude that federal law must forever and always accept state law definitions. All it needs to do is recognize that defining marriage is a traditional function of the states, not the federal government, and, as a consequence, there is no federal interest sufficient to justify DOMA. [...]