In August 2005, the Competitive Enterprise Institute (CEI), a conservative advocacy organization, filed a lawsuit in Louisiana challenging the legality of the 1998 Master Settlement Agreement (MSA). The suit alleges that the MSA, under which the states receive monetary payments and the four major tobacco companies are insulated from price competition, violates the Compact Clause and other provisions of the U.S. Constitution. This lawsuit threatens to unravel of one of the most significant opportunities to improve public health in United States history. We consider the merits of the lawsuit, the problems with the MSA that it highlights, and the potential consequences of the suit for public health.