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.

Health-care backers understand this and—like Lewis Carroll’s Red Queen insisting that some hills are valleys—have framed the mandate as a “tax” rather than a regulation. Under Sen. Max Baucus’s (D., Mont.) most recent plan, people who do not maintain health insurance for themselves and their families would be forced to pay an “excise tax” of up to $1,500 per year—roughly comparable to the cost of insurance coverage under the new plan.

But Congress cannot so simply avoid the constitutional limits on its power. Taxation can favor one industry or course of action over another, but a “tax” that falls exclusively on anyone who is uninsured is a penalty beyond Congress’s authority.