After considerable debate, the Founding Fathers elected to give the new federal government the power of regulating commerce among the several states. We’ve all seen what’s become of that power, but in the beginning, giving the federal government the ability to regulate interstate commerce—literally, to “make regular”—made good sense as a way to avoid the otherwise inevitable collective-action problems, like trade wars and anti-competitive jockeying for monopolies. The goal was to ensure that federal law would not permit or bestow any unfair competitive advantage to any one state or group of states over the others. Throughout much of our nation’s history, the federal government has, for the most part, succeeded at this particular goal. Thanks to the Professional and Amateur Sports Protection Act of 1992 (PASPA), however, Congress’s power to keep states from obtaining unfair advantages is being used to grant some states (most notably Nevada, but also Oregon, Montana, and Delaware) an unfair advantage: a special right to license gambling, which PASPA prohibits to other states. In 2012, New Jersey Governor Chris Christie signed a sports-gambling bill into law, and as a result was sued by the NCAA, NFL, MLB, NHL, and NBA, who believed that additional sports betting would result in corruption and game-fixing. Christie defended his actions by arguing that PASPA violates the 10th Amendment by restricting New Jersey’s right to govern itself, and also that it violates the equal-sovereignty doctrine by giving an unfair advantage on certain states. The federal district court and the U.S. Court of Appeals for the Third Circuit failed to recognize these constitutional flaws, so New Jersey has now asked the Supreme Court to hear its case. Cato has joined the Pacific Legal Foundation on a brief supporting New Jersey’s petition. We explain that the principle of equal sovereignty was central to the creation of Congress’s power to regulate interstate commerce, and that conferring state-specific advantages is precisely opposite to the commerce power that the Framers created. We think it important that the Supreme Court hear this case because it offers an excellent opportunity to explain the equal-sovereignty doctrine and how it furthers federalism, and to provide guidance as to the scenarios in which the doctrine applies. Congress shouldn’t be able to pick winners and losers among the states.