The U.S. Supreme Court ruled that courts must consider customers on both sides of credit card transactions—merchants and cardholders—when evaluating antitrust claims, from the outset. In so doing, the court affirmed the U.S. Court of Appeals for the Second Circuit’s rejection of claims that anti-steering provisions in American Express’s merchant agreements violated §1 of the Sherman Act. Ohio v. American Express Co., 138 S.Ct. 2274 (2018).

Proper adjudication of antitrust disputes requires careful study and exploration of the economic markets at issue. As such, developments in economic scholarship have often informed the evolution of antitrust jurisprudence. This decision continues in that tradition. The opinion is also significant for affirming the three-step burden-shifting framework lower courts devised for applying the rule of reason, describing how the rule applies to two-sided transaction platforms, and requiring plaintiffs to define a relevant market when challenging vertical conduct.

Background