I didn't have much space in my column about the proposed individual health insurance mandate to discuss its constitutionality. Given the way the Supreme Court has interpreted the Commerce Clause since the New Deal, it probably would uphold a federal requirement that every American buy medical coverage, on the theory that individual decisions about whether to buy insurance, in the aggregate, have a substantial impact on interstate commerce. But that does not mean such a mandate would be constitutional—i.e., that it should be upheld. The misbegotten idea that regulating interstate commerce includes regulating (or prohibiting) any activity (or inactivity) that might affect interstate commerce gives Congress carte blanche to do anything not explicitly prohibited by the Constitution and renders its enumerated powers superfluous.
Even given the Supreme Court's rulings in this area, it would break new ground to say that the decision to refrain from engaging in intrastate commerce (by going without health insurance) triggers the clause authorizing Congress to regulate interstate commerce. Misguided as they were, both Wickard v. Filburn, the 1942 case involving wheat, and Gonzales v. Raich, the 2005 case involving medical marijuana, at least dealt with production of a commodity traded in interstate commerce (although both the wheat and the marijuana were grown for personal use and never crossed state lines). In this case, by contrast, the "act" triggering federal involvement is not commerce, not production, and not even an act. It is the failure to engage in a particular transaction. The difference might not give pause to a majority of the Court, but it is discernible.
In a Washington Post op-ed piece last month, Bush administration lawyers David Rivkin and Lee Casey argued that the health insurance mandate would exceed the power granted by the Commerce Clause as the Supreme Court has defined it. Washington and Lee law professor Timothy Jost and Georgetown University law professor Randy Barnett (who represented Angel Raich in the medical marijuana case) debated that proposition at The Politico last week. Barnett, Ilya Somin, and Jonathan Adler discuss the proposed mandate's constitutionality at The Volokh Conspiracy here, here, and here. Peter Urbanowicz and Dennis G. Smith deal with the issue at greater length in a recent Federalist Society paper (PDF).