The rule stops the cable company from owning more than 30 percent of the nation's pay-TV market. Comcast, the nation's No. 1 cable company, controlled about 27 percent of the market when the rule passed. The company's share of the pay-TV market has shrunk slightly, to 26.2 percent, partly because it has lost customers to competitors.

Comcast filed an appeal in the U.S. Court of Appeals for the District of Columbia Circuit. The Philadelphia company said in its March 12 filing that the order was "arbitrary, capricious, and an abuse of discretion."

"The record at the FCC provided absolutely no support for a horizontal ownership cap of 30 percent - a position that has been supported by the courts," David L. Cohen, executive vice president of Comcast, said in a statement yesterday.

An FCC spokeswoman declined to comment.

FCC Chairman Kevin Martin, a Republican, secured the 3-2 vote with an alliance with Democratic commissioners Michael Copps and Jonathan Adelstein.

Andrew Jay Schwartzman, president of Media Access Project, a public-interest law firm, supports the rule. As Comcast grows bigger, the company has greater control over setting prices, influencing the programming markets, and keeping out competitors, he said.

"We think the FCC has a solid basis for this 30 percent ruling, and we will be going to court in support," he said.