The ITC imposed the ban in June 2007 because it found that some Qualcomm chips infringed on a battery-saving technology patent owned by Broadcom Corp., a rival maker of cell phone chips. The ban was stayed in September 2007 by the U.S. Court of Appeals for the Federal Circuit, pending appeal.

In its opinion Tuesday, the court said the ITC lacked the authority to ban the imports of phones made by companies such as Motorola Inc. and Samsung Electronics Corp., even if their phones included Qualcomm chips. It sent the case back to the commission.

"Qualcomm is very pleased with the Court's opinion," said Don Rosenberg, executive vice president and general counsel of Qualcomm. "In effect, the Court has disapproved Broadcom's tactic of attacking the wireless industry, including handset manufacturers and wireless operators, without providing them with the opportunity to defend themselves in the action."

Broadcom spokesman Bill Blanning said the company was pleased that the appeals court affirmed the validity of its patent and that it had been infringed.

"We look forward to addressing this issue upon remand to the ITC. We will continue to pursue other avenues for enforcement against infringement of our intellectual property by Qualcomm," Blanning said.

Qualcomm shares fell $1.98, or 4.7 percent, to $40.32 on Tuesday. Broadcom shares fell $1.27, or 7.8 percent, to $15.10.