Some have argued that it does not matter whether the individual mandate is a constitutional exercise of the power to regulate “commerce . . . among the several states” because the mandate — or, more properly, the penalty for failing to comply with the requirement to obtain health insurance — is within Congress’ power to tax. But is this so? Steven J. Willis and Nakku Chung of the University of Florida have a forthcoming article in Tax Notes in which they argue that if the penalty is a tax, it is a “direct tax” for purposes of Article I, section 9 and is therefore unconstitutional. Specifically, they argue that the tax is neither an income tax nor an excise tax, nor a proportional capitation tax, and is therefore not a constitutional exercise of the federal taxing power. (Hat tip: Lawrence Solum)