Comcast is asking an appeals court to rule that the Federal Communications Commission lacked the authority to sanction the company for violating net neutrality principles by throttling peer-to-peer traffic.

"This historic action," Comcast argued, referring to the FCC's order, "was not undertaken pursuant to any federal statute, regulation, or precedent governing the network management practices."

Last year, a divided FCC ruled 3-2 that Comcast's pattern of interfering with high-bandwidth peer-to-peer traffic violated principles that had been set out in a 2005 Internet policy statement. That document said that service providers should treat all lawful applications equally, and that consumers should have access to all lawful content of their choice. The commission directed Comcast to stop singling out peer-to-peer traffic for special treatment, but did not impose a fine.

Consumer advocates hailed the landmark decision for clearly affirming that the FCC would enforce neutrality principles. But as a practical matter, the ruling was seen as having little effect on Comcast because the company had already promised to move to a protocol-agnostic traffic management system.

Comcast appealed the FCC's ruling to the U.S. Court of Appeals for the D.C. Circuit, and last month, the cable company filed its brief. The company argues that the FCC cannot enforce its 2005 policy statement because it was never officially enshrined in law, either as a statute or a regulation.

The case has drawn the interest of a number of outside groups, ranging from advocacy organizations to media companies. Last week, NBC Universal and the National Cable & Telecommunications Association also filed papers asking the appellate court to vacate the FCC's order.

They argue that prohibiting ISPs from blocking peer-to-peer traffic could hinder efforts to thwart piracy. "The record before the FCC established that P2P [peer-to-peer] technologies are used today primarily to facilitate the exchange of massive amounts of copyright-infringing content on the Internet," the groups assert in their appellate papers.

They add that service providers who "deploy measures to reduce the amount of illegal content transmitted via their networks should not be penalized if these measures block or delay a small amount of non-infringing material."

Comcast's traffic-shaping techniques came to light in 2007, after some subscribers noticed they were having difficulty uploading files. Tests by The Associated Press and the Electronic Frontier Foundation subsequently confirmed that Comcast was systematically throttling peer-to-peer traffic. The result was that people found themselves unable to share a host of material, including works in the public domain -- like the King James Bible.

Comcast eventually acknowledged that it sometimes interfered with peer-to-peer connections, but the company said it did so in order to manage congestion on its network. The revelations also sparked net neutrality advocates Free Press and Public Knowledge to file a complaint with the FCC.

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