In the Wall Street Journal, lawyers David R. Rivkin and Lee A. Casey write:

Policy problems aside, by transforming the mandate into a tax to avoid one set of constitutional problems (Congress having exceeded its constitutionally enumerated powers), the court has created another problem. If the mandate is an indirect tax, as the Supreme Court held, then the Constitution’s “Uniformity Clause” (Article I, Section 8, Clause 1) requires the tax to “be uniform throughout the United States.” The Framers adopted this provision so that a group of dominant states could not shift the federal tax burden to the others. It was yet another constitutional device that was simultaneously designed to protect federalism and safeguard individual liberty.

Read more: The Opening for a Fresh ObamaCare Challenge.

Via Jonathan Adler: The Volokh Conspiracy » The Uniformity Clause – Another ObamaCare Challenge?.