In a setback for the Federal Communications Commission (FCC), a federal court issued a ruling recently that may force cable companies to share their high-speed Internet, or broadband, networks with competing Internet service providers.

The decision, issued by a three-judge panel of the Court of Appeals for the Ninth Circuit, found that the FCC erred in an earlier ruling that effectively absolved cable companies of any obligation to make their lines accessible to competitors.

Internet access providers who sued to get the right to lease those lines and offer competing services over them said the court decision would give consumers more choice when shopping for a provider of high-speed Internet service. “This will help drive prices down and quality of service up; it will drive broadband deployment,” said Dave Baker, vice president for law and policy at Earthlink, an Internet service provider and a plaintiff in the lawsuit.

The FCC said it would appeal the case. Michael K. Powell, the chairman of the FCC, said in a statement that the decision would hurt efforts to develop a national policy on high-speed Internet services.

Despite claims of victory by the cable industry’s competitors, telecommunications lawyers said the implications of the 39-page ruling might not be clear for some time because the decision did not specifically require cable companies to lease their lines to competitors. Rather, the court ruled that the FCC was wrong in the way it categorized cable broadband services for regulatory purposes.

The FCC’s approach toward broadband regulation — for both cable companies and telephone companies — is to permit the major players to build their high-speed Internet infrastructure without requiring them to open their networks to competitors.