Those here know the importance to the government of successfully articulating a "limiting principle" to its argument--in short, being able to explain why the Court's upholding the minimum coverage provision will not effectively grant Congress a general police power.
So much has been written on this subject that I hesitate to say any more. But there is a little part of this discussion that has bothered me, so I just can't help myself.
My small point is this: The government's proposed limiting principle is that the minimum coverage provision is necessary to the effectiveness of a regulatory scheme that, taken as a whole, plainly regulates interstate commerce. Only provisions that are so necessary (if they do not directly regulate interstate commerce themselves) are within Congress's authority.
This probably seems obvious. But too often the government's articulated limiting principle has been mishcharacterized as some sort of ad hoc, jury-rigged set of factors pegged to the distinctiveness of the health care market (e.g., that almost is everyone is in that market, that the costs are exorbitant, that they are unpredictable, and that the absence of insurance thus results in massive cost-shifting). These are all reasons that the government believes that an individual mandate is truly critical here, and thus easily satisfies the standard of necessity. It is also a means of showing that many other purchasing mandates would not be "necessary."
But these factors are not a "limiting principle" themselves. The limiting principle is "necessity," taken straight from the text of Article I, section 8, clause 18. The oft-cited factors are merely the factual bases for arguing that the minimum coverage provision satisfies this requirement of necessity.
Of course, one might be dissatisfied with this principle on the grounds that, in practice, it really is not a limit. No doubt, the Court's review of "necessity" under the Necessary and Proper Clause has been quite deferential since M'Culloch, and there is a decent argument that it is difficult to devise any sort of judicially manageable standard that operationalizes "necessity" so as to have any teeth. Fair points, to be sure. Thus, Ilya Somin would argue (I think) that if this is your limiting principle, it leads us down a slippery slope justifying all sorts of purchasing mandates. (I'm not sure I agree, but I certainly see the point.)
My only point here is that the "limiting principle" itself proposed by the government is indeed principled. It is not ad hoc or gerrymandered to suit this case (as Justice Scalia seemed to suggest at oral argument). In other words, the problem is not really the principle itself--a principle grounded in the text of the Constitution, and well explained by Justice Scalia in his Raich concurrence. Rather, the precise problem concerns fears about the judicial enforceability of the standard of necessity.