PHILADELPHIA — A federal appeals court ruled Monday that Delaware's plan to offer sports betting would violate a 1992 federal ban on sports wagering.

The court in Philadelphia ruled after hearing almost two hours of arguments from attorneys for Delaware and for professional sports leagues and the NCAA, who opposed the plan.

Delaware claimed it was exempt from the federal ban because it ran a sports lottery in 1976. The leagues claim the exemption does not allow Delaware to offer bets on single games or on sports other than professional football, but attorneys for the state argued otherwise.

The leagues were challenging the denial of an injunction that would have prevented the betting from beginning next month. Attorneys for Delaware argued that the leagues had not met the requirements for an injunction.

But instead of ruling on the injunction, the appeals court turned directly to the league's claim that the sports betting would violate federal law.

During Monday's arguments, Judge Theodore McKee questioned what would happen if the state was allowed to begin sports betting in September, then have it declared illegal by several months later. Individual bettors will have lost hundreds or thousands of dollars on what essentially was an illegal state scheme, he noted.

"What happens if you're wrong?" McKee asked Andre Bouchard, an attorney representing the state.

"Caveat emptor," Bouchard replied, citing the Latin admonition of "buyer beware."