The rules that American Express (AXP) imposes on merchants to prevent them from steering customers to low-cost ways of paying are unlawful under a U.S. antitrust law, a federal judge ruled on Thursday.
U.S. District Judge Nicholas Garaufis of Brooklyn, who last year oversaw a trial in which the U.S. Justice Department and 17 states accused Amex of harming competition, said he would come up with a remedy at a later date.
The credit card company said in a statement Thursday that it is disappointed by the decision.
Amex has defended its merchant rules, and has said its business could suffer a “material adverse effect” if it loses the case.
Shares of Amex fell sharply following news of the decision.