The United States has 13 federal courts of appeals, called circuit courts. When two or more of these courts interpret the same federal law differently, the result is a circuit split. A circuit split means the same activity is legal in some states and illegal in others, depending on which circuit the state is in. The Supreme Court typically steps in so that federal law is applied consistently nationwide. In the Kalshi prediction market cases, the Third Circuit (covering Pennsylvania, New Jersey, and Delaware) ruled 2-1 for Kalshi in April 2026. If the Ninth Circuit (covering California, Nevada, Arizona, and six other western states) rules for the states, a direct circuit split would exist and Supreme Court review would become nearly automatic.