The most recent reports on why Roberts switched sides and decided to uphold the individual mandate contain a very telling nugget of information: According to Salon, the first three-fourths of the dissenting opinion was written in Roberts’s chambers. If true, this tends to support my suspicion that the real reason Roberts switched sides was not politics or sensitivity to criticism, but an issue of constitutional law. It seems plausible that after reaching a five-vote consensus to strike down the mandate, a serious impasse may have developed over the issue of severability: what to do with the rest of the law once the individual mandate was struck down. Sure enough, the last fourth of the dissent — the part Roberts reportedly did not write — focuses on precisely this issue.
In researching the Supreme Court amicus brief I wrote with Richard Epstein and Cato’s Ilya Shapiro on severability, I reviewed virtually every major Supreme Court severability decision back to Marbury v. Madison (1803). Looking back on those decisions, I am certain that striking down the individual mandate in Obamacare would have presented the Court with the most complex and difficult severability analysis in its history. Indeed the case seems almost tailor-made to test the limits of the Court’s severability doctrine to the breaking point. This is because (as we argued in our brief) the individual mandate is so interwoven with the other key provisions of the law (Titles I and II) that they could not have functioned as intended without the mandate. The 11th Circuit Court of Appeals decision to strike the mandate and leave the rest of the law in place was clearly incorrect. So the only good option to striking down the whole law was to strike down the core provisions and leave a shell of ancillary provisions in place. But Justice Antonin Scalia made it very clear during oral argument he would not support that outcome.
Given the organic and impossibly interwoven nature of Obamacare, the dissent concluded that the whole law must be struck down, out of deference to the prerogatives of Congress. Now, there is no way to tell whether one or more of the four dissenters held fast to that position from the start. But it’s possible, and Roberts might have argued — entirely in keeping with the Court’s current (and I believe, flawed) severability doctrine — that deference to Congress required striking down only the bare minimum element necessary to cure the constitutional defect and leave the rest of the law in place. He may have preferred to affirm the 11th Circuit ruling, or strike down one or two other provisions with the mandate, while leaving most of the rest in place. In short, the dissent might have refused to go along with his “best offer” on partial invalidation.
Roberts may have concluded that there was no prospect of five votes for a defensible outcome on the issue of severability, and switched sides in order to avoid reaching the issue at all. This is all pure speculation, of course, but it’s at least as plausible as all the other speculation you’ve heard in the last week about why Roberts voted the way he did.