As I indicated in my earlier post, Randy Barnett's upcoming Hayek lecture at NYU (the text of which you can find here) is a terrific presentation of the constitutional arguments against the individual mandate. I have now read through it twice, and I think it does an exceptional job of presenting the best case possible, under existing law, as to why ACA 1501(b) might be found unconstitutional.
One of the most interesting aspects of Barnett's arguments is captured in its title, Commandeering the People. To oversimplify a bit, Barnett argues that the anti-commandeering principle articulated by the Supreme Court in New York and Printz can be carried over to apply to "economic mandates" imposed on private individuals. After all, the Tenth Amendment recognizes the People as a sovereign just as much as it recognizes the states. Thus, just as the mandates directed at the states in New York and Printz were an "improper" means of implementing the commerce power (for purposes of the Necessary and Proper Clause), so, too, is the minimum coverage requirement imposed by 1501.
This is an interesting and quite creative argument, and (to my knowledge) a highly original contribution by Barnett. It also, as he notes, taps into the what many Americans find objectionable about 1501 -- that it simply commands certain Americans to engage in commercial transactions with private third parties. Still, I think there are some significant problems with the analogy that ultimately render it inapposite.
Most important, the anti-commandeering principle does not apply to all coercive mandates imposed by Congress on the states. Indeed, the vast majority of such mandates are perfectly constitutional--those imposed by such laws as the Fair Labor Standards Act, the Americans with Disabilities Act, the Age Discrimination in Employment Act, Title VII of the Civil Rights Act, a raft of environmental laws, and many, many more. All of these laws require states to do certain things. They are mandates. And yet, they are not "commandeerings" that violate the structural principles of federalism.
Why are all these mandates constitutional? Because they regulate the states essentially in their proprietary capacities: their functions as employers, polluters, or the like. In other words, these laws do not regulate the the states' functions as regulators or governors of their own citizens--in their sovereign capacities. This is what the laws in New York (a law commanding the states to enact and enforce legislation) and Printz (a law commanding state law enforcement officers to enforce a federal statute) did.
Thus, the anti-commandeering principle to which Barnett seeks to analogize ACA 1501 specifically concerns mandates imposed on the sovereign powers of the states, their powers to govern or regulate. It is not a principle about commands or mandates more generally. And, by definition, it is not really analogous to mandates imposed on private individuals, because private individuals lack any authority to govern or regulate (even if we might describe the People, more abstractly, as the ultimate sovereign).
In fine, nothing in New York or Printz indicates that coercive mandates to engage in certain forms of activity are "improper" legislative means under the Necessary and Proper Clause. Particular mandates might be, but not mandates per se.
Barnett might distinguish statutes like the FLSA and Title VII on the ground that they do not really mandate that states engage in any activity. Rather, those statutes merely regulate the terms of employment once a state has made the choice to hire a certain number of employees. But what state could really not hire employees? Realistically, there is no choice. Barnett might also argue that statutes like the FLSA and Title VII, unlike ACA 1501, regulate how an activity is engaged in, rather than mandating that the activity be performed in the first place. For example, Title VII dictates how one is to treat employees (by not discriminating against them on certain bases), but it does not require states to hire employees in the first place. I may be missing something, but this distinction seems entirely semantic. Suppose a state would like to pay its janitors $6.00 per hour. The FLSA dictates that it must pay $7.25. We can say that this regulation only concerns how the states are to engage in employment. But we can just as easily say that the FLSA mandates that the state pay its janitors an additional $1.25 per hour -- that it forces the state into activity it would otherwise avoid.
All of this said, I think it is still quite plausible to argue (as Barnett does) that the ACA's minimum coverage provision is not a "proper" use of the commerce power under the Necessary and Proper Clause. This is his larger point, and the analogy to the anti-commandeering decisions is only in service of that argument.
My only point here is that I do not think the analogy to New York and Printz advances his argument, other than to show, more generally, that some legislative means can be improper even when they might be considered "appropriate" or "conducive."