There is, of course, currently an impressive flurry of online discussion about Gonzales v. Carhart -- to which I am paying close attention, it bears very much upon my forthcoming article on informed consent and abortion. I have many thoughts about this decision and its ultimate import, but for now I'll settle for noting the latent federalism question. As Justice Thomas noted in his concurrence, the parties and the lower courts did not raise whether the Partial-Birth Abortion Ban Act was valid Commerce Clause legislation, and so the Supreme Court didn't either.
Until PBABA the Congress, though monkeying with federal funding provisions, had otherwise stayed out of the abortion issue, and it's far from clear whether this kind of law could survive recent federalism precedents. But liberal Democrats have decided to jump into the game, too, reintroducing a a bill from the 109th Congress that would attempt to codify Roe, in all its pre-Casey, strict-scrutiny glory, in the U.S. Code. This bill didn't go anywhere before, and its still might not now, even with the fresh Carhart II furor. After all, the PBABA had significant support from Democrats. It may be that this new bill, if passed, would not pass federalism muster, and neither would the PBABA. Yet public opinion appears to favor uniform, national rule-making on these hot-button issues.
Now, that opinion might change with the new Congressional majority, or new Supreme Court decisions, or whathaveyou. It seems to me that, outside that intellectual arena, when we talk about federalism and "leaving things to the states," the argument is typically a cipher for substantive policy preferences -- i.e., those supporting abortion restrictions favor "leaving it to the states" because the trend in the states was toward restricting abortion; those supporting recognition for same-sex couples favor "leaving it to the states" because there is a long-term liberalizing trend there, in contrast to the proposed Federal Marriage Amendment.
Alternatively, appeals to federalism might be a reflection of our ambivalence about the substantive issue (i.e., we want to have it both ways, for now). But it's hard for most of us to care about federalism for its own sake; instead we argue it because it sounds eminently reasonable, and because it may appeal to the ambivalent.
Having lost on the substantive issues, reproductive rights groups might now launch a federalism challenge to PBABA, and might win. But they'll have a hard time selling the federalism line to their constituents or to anyone else. Perhaps federalism is most important when it comes to controversial social issues (as opposed to true economic regulation) -- but today, do many of us really care?