WASHINGTON – Comcast Corp. is appealing an FCC ruling that the company is improperly blocking customers' Web traffic, triggering a legal battle that could determine the extent of the government's authority to regulate the Internet.

In a precedent-setting move, a divided Federal Communications Commission last month determined that the company is violating a federal policy that guarantees unfettered access to the Internet.

Comcast challenged the FCC decision Thursday in the U.S. District Court of Appeals in Washington.

Comcast executive vice president David L. Cohen said in a statement that the company is seeking “review and reversal” of the FCC order and that the commission's action was “legally inappropriate and its findings were not justified by the record.”

The Comcast case arose from complaints by users of a type of “file-sharing” software often used to download large data files, usually video.

Tests by The Associated Press and others found that file-sharing transmissions were aborting prematurely. It was later discovered that the company was cutting off transfers without informing customers.

The FCC noted Comcast's network management practices were “discriminatory and arbitrary” and that the company's practices “contravene industry standards and have significantly impeded Internet users' ability to use applications and access content of their choice.”

The agency also noted that the type of traffic Comcast is blocking has become “a competitive threat” to cable operators because it is used by people to view high-quality video that they “might otherwise watch (and pay for) on cable television.”

While the FCC action did not include a fine, it does require Comcast within 30 days to disclose the details of its “discriminatory network management”; submit a compliance plan describing how it intends to stop these practices by the end of the year; and disclose to customers and the commission its new plan.

Cohen said Thursday that the company will comply with the FCC's order. Prior to the FCC action, the company had said it will switch to a management technique that treats all users the same by the end of the year.

Meanwhile, a public interest law firm representing two consumer groups and a California company that benefits from the type of file-sharing software targeted by Comcast filed appeals in New York, Philadelphia and San Francisco.

The legal challenges, filed last week, ask the court to force Comcast to cease its management practices immediately rather than by the end of the year.

The actions were more likely an attempt to avoid the District of Columbia court circuit, which is perceived as friendly to industry. If the cases are consolidated, the venue will be decided by lottery.

The plaintiffs are Consumers Union, in Yonkers, N.Y.; PennPIRG in Philadelphia; and Vuze Inc. of Redwood City, Calif. They are represented by the Media Access Project in Washington.

Comcast has said that it has delayed traffic, not blocked it – and that the FCC's so-called network-neutrality “principles” are part of a policy statement and not enforceable rules.

The FCC action came about in response to a complaint filed by public interest group Free Press and others.

Since the FCC vote, Comcast has announced that beginning Oct. 1, it would institute a broadband usage cap of 250 gigabytes per month for all residential customers. Comcast says to exceed that limit a customer would have to send 50 million e-mails or download 125 standard-definition movies.