Two U.S. congressmen have proposed legislation to label satellite providers of incendiary TV stations as terrorist organizations -- the latest attempt by lawmakers to prevent radical anti-American propaganda from hitting the airwaves, even abroad.

The bill, authored by Rep. Gus Bilirakis, R-Fla., and Rep. Joseph Crowley, D-N.Y., seeks to punish satellite companies that carry channels that are mouthpieces for known terrorist groups like Hezbollah and Hamas -- stations they say incite their audiences to commit acts of terrorism against the United States.

But some free speech advocates question the constitutionality and consequences of the legislation, arguing that such modes of communication are a useful tool in monitoring terrorist movements.

"The constitutionality of such a statute is uphill," said Harvey Silverglate, a civil liberties attorney with the Boston-based law firm Zalkind Rodriguez Lunt & Duncan LLP.

"It runs against the grain of the way in which our government has generally treated common carriers. The telephone company, for example, isn't responsible for anything said and done on the phone lines."

The legislation, if passed, will label as terrorists those satellite providers that "knowingly and willingly contract with entities designated as specially designated global terrorists" under U.S. law.  The administration will have to administer an annual report that includes research on the content of such broadcasts. 

"The objective is to shut down these terror tools," Bilirakis told FOXNews.com on Thursday.  "There are many children in these countries who are watching, and I don't want them to be susceptible to recruitment."

Of chief concern to lawmakers are satellite carriers ArabSat and NileSat, which transmit stations like al-Aqsa, al-Manar TV and al-Rafidayn TV -- an anti-Iraqi government channel -- across the Arab world.

Bilirakis said that while the legislation does not include provisions on how, specifically, satellite providers will be punished, he said he hopes it will eventually lead to sanctions -- including sanctions on the countries that are state sponsors of such networks. 

"This is a starting point," Bilirakis said. 

The proposal also calls for governments and private investors who own shares in these satellite companies to oppose transmissions of telecasts by the three networks.

"Al-Manar and Hezbollah are indistinguishable," said Mark Dubowitz, executive director for the Foundation for Defense of Democracies, who has worked to lobby satellite providers to dismantle stations that aid and abet terrorist groups.

The U.S. government designated al-Manar a terrorist organization in March 2006 -- marking the first time the United States declared a media operation a terrorist group. U.S. officials determined al-Manar was helping to recruit and raise money for Hezbollah, and conducting pre-attack surveillance on behalf of the terrorist group.

"Al-Manar officials were using their press passes to actually case out potential terrorist targets," Dubowitz said. 

Nine of out 12 satellite companies have stopped transmitting al-Manar, including four carriers in Europe and three in Australia, Brazil, and Hong Kong. But NileSat, based in Egypt, and ArabSat, which is Saudi-owned, continue to broadcast the channel. 

"The introduction of the legislation sends a powerful message to the Saudis and the Egyptians that the U.S. government is taking very seriously the issue of terrorist media," said Dubowitz.

Silverglate said that pressuring carriers to dismantle such stations forces the anti-American propaganda underground -- making it difficult for terrorism experts to monitor the quality and quantity of such propaganda.

"I think it's a very bad idea to expand the definition of aiding terrorism to those organizations that supply the modes of communication," he said. "Shutting off the modes of communication leaves us all in the dark. We're not only entitled to know what's going on, we have an obligation to know."

But Dubowitz disagreed.

"These satellite providers have crossed all red lines with respect to free speech," he said. "They're doing more than yelling fire in a crowded movie theater. They're providing the match, the gasoline and the arsonist."