Comcast's appeal, filed in Sept. 2008, set up a legal showdown over whether the FCC has the power to enforce its previous net neutrality rules, or whether new legislation is needed by Congress to give it such authority.

On Monday, several prominent law professors including Harvard's Larry Lessig, Columbia's Tim Wu and Yale's Jack Balkin, urged the U.S. Court of Appeals in Washington, D.C. to uphold the FCC's order.

"Although the Order takes only modest steps, reversing the Order could pose significant threats to the Internet as we have always known it, and to its features that federal policy has sought to promote," the professors wrote. "Specifically, reversing the Order would reduce the Internet's ability to serve as an open platform for innovation, economic growth and democratic discourse."

Additionally, Free Press, a Washington, D.C.-based pro-net neutrality group, filed a brief with the court, along with several other organizations including the Consumer Federation of America, Consumers Union, Public Knowledge and the Open Internet Coalition, supporting the FCC's order.

"We strongly support the FCC's action to protect consumers from secret, illegal Internet blocking," Chris Riley, policy counsel at Free Press, said in a statement. "This case is about a federal agency punishing violations of federal law and policy. The FCC acted well within its authority as established by Congress and multiple federal courts."

"Comcast's arguments to the court are legal acrobatics attempting to prevent the FCC from enforcing the law," Riley added. "But Comcast must answer for its actions. Its illegal blocking demonstrates why the FCC must take action to protect the free and open Internet and why stronger Net Neutrality rules, like the ones recently proposed by FCC Chairman Julius Genachowski, are urgently needed to protect consumers."

Comcast did not return a request for comment on the briefs.

The FCC voted 3-2 last year to punish Comcast after concluding that the cable giant had run afoul of the agency's 2005 Internet Policy Statement, which made network neutrality official government policy. Comcast, however, has long argued that the FCC lacks the authority to enforce that principle.

"In order to enforce something, an agency must be enforcing a rule that has force of law," Comcast spokesperson Sena Fitzmaurice said when the company's appeal was filed. The FCC's internet policy statement does not meet that test, she said.

In voting to sanction the company, FCC Chairman Kevin Martin argued that enforcement of the internet policy is within the agency's purview. "I am pleased that a majority has agreed that the Commission both has the authority to, and in fact will, stop broadband service providers when they block or interfere with subscribers' access," Martin said at the time.

Even as it filed its appeal, Comcast said it intended to comply with the FCC orders, which "essentially codify the voluntary commitments that we have already announced." In March 2008, facing intense FCC and public pressure, Comcast said it would move to a "protocol agnostic" network-management approach and not discriminate against any type of online traffic, say providing slower service for video downloads from YouTube, over its own broadband Internet video programming.

Comcast has said its suit is less about the particulars of its case, and more about the scope of FCC authority moving forward. The cable giant has never disputed that the FCC has the authority to regulate Internet service providers, but said "we are compelled to appeal because we strongly believe that, in this particular case, the commission's action was legally inappropriate and its findings were not justified by the record."

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