Julius Genachowski, the chairman of the F.C.C., had said previously that if the agency lost the Comcast case, he would seek to find other legal authority to implement consumer protections over Internet service. In a statement, the F.C.C. said it remained “firmly committed to promoting an open Internet.”

While the court decision invalidated its current approach to that goal, the agency said, “the court in no way disagreed with the importance of providing a free and open Internet, nor did it close the door to other methods for achieving this important end.”

The concept of equal access for all Internet content is one that people who favor some degree of F.C.C. regulation say is necessary not only to protect consumers but also to foster innovation and investment in technology.

“You can’t have innovation if all the big companies get the fast lane,” said Gigi B. Sohn, president of Public Knowledge, which advocates for consumer rights on digital issues. “Look at Google, eBay, Yahoo — none of those companies would have survived if 15 years ago we had a fast lane and a slow lane on the Internet.”

The court’s ruling could potentially affect content providers like Google, which owns YouTube, a popular video-sharing service. Content providers fear that Internet service companies will ask them to pay a fee to ensure delivery of material like high-definition video that takes up a lot of network capacity.

Google declined to comment directly on the ruling but pointed to the Open Internet Coalition, of which it is a member. The coalition’s executive director, Markham Erickson, said the decision “creates a dangerous situation, one where the health and openness of the Internet is being held hostage by the behavior of the major telco and cable providers.”

Sam Feder, a lawyer who formerly served as general counsel for the F.C.C., said that the court’s decision “is the worst of all worlds for the F.C.C.” He said the opinion was written narrowly enough that it was unlikely to be successfully appealed, while also raising enough possibilities of other ways that the F.C.C. could accomplish the same goals that it was unlikely to inspire Congressional action to give the agency specific regulatory authority over the Internet.