Former Justice Department attorneys David B. Rivkin Jr. and Lee A. Casey say yes. As they argue in today's Wall Street Journal:
The Supreme Court construes the commerce power broadly. In the most recent Commerce Clause case, Gonzales v. Raich (2005) , the court ruled that Congress can even regulate the cultivation of marijuana for personal use so long as there is a rational basis to believe that such "activities, taken in the aggregate, substantially affect interstate commerce."
But there are important limits. In United States v. Lopez (1995), for example, the Court invalidated the Gun Free School Zones Act because that law made it a crime simply to possess a gun near a school. It did not "regulate any economic activity and did not contain any requirement that the possession of a gun have any connection to past interstate activity or a predictable impact on future commercial activity." Of course, a health-care mandate would not regulate any "activity," such as employment or growing pot in the bathroom, at all. Simply being an American would trigger it.
Law professor and Volokh Conspiracy blogger Jonathan Adler takes a different view:
There is a strong temptation to believe that every onerous or oppressive government policy is unconstitutional Were it only so. Even were the federal government confined to those powers expressly enumerated in the text, it would retain ample ability to enact many bad ideas into law, and current precedent is far more permissive. Opponents of current health care reform proposals should defeat them the old fashioned way, through the political process, and not depend upon salvation from the courts.