By David Segal and Aaron Swartz

When it really matters to them, Congressmembers can come together –– with a panache and wry wit you didn't know they had. As banned books week gets underway, and President Obama admonishes oppressive regimes for their censorship of the Internet, a group of powerful Senators –– Republicans and Democrats alike –– have signed onto a bill that would vastly expand the government's power to censor the Internet.

The Combating Online Infringement and Counterfeits Act (COICA) was introduced just one week ago, but it's greased and ready to move, with a hearing in front of the Judiciary Committee this Thursday. If people don't speak out, US citizens could soon find themselves joining Iranians and Chinese in being blocked from accessing broad chunks of the public Internet.

Help us stop this bill in its tracks! Click here to sign our petition.

COICA creates two blacklists of Internet domain names. Courts could add sites to the first list; the Attorney General would have control over the second. Internet service providers and others (everyone from Comcast to PayPal to Google AdSense) would be required to block any domains on the first list. They would also receive immunity (and presumably the good favor of the government) if they block domains on the second list.

The lists are for sites "dedicated to infringing activity," but that's defined very broadly –– any domain name where counterfeit goods or copyrighted material are "central to the activity of the Internet site" could be blocked.

One example of what this means in practice: sites like YouTube could be censored in the US. Copyright holders like Viacom often argue copyrighted material is central to the activity of YouTube, but under current US law, YouTube is perfectly legal as long as they take down copyrighted material when they're informed about it –– which is why Viacom lost to YouTube in court.

But if COICA passes, Viacom wouldn't even need to prove YouTube is doing anything illegal to get it shut down –– as long as they can persuade the courts that enough other people are using it for copyright infringement, the whole site could be censored.

Perhaps even more disturbing: Even if Viacom couldn't get a court to compel censorship of a YouTube or a similar site, the DOJ could put it on the second blacklist and encourage ISPs to block it even without a court order. (ISPs have ample reason to abide the will of the powerful DOJ, even if the law doesn't formally require them to do so.)

COICA's passage would be a tremendous blow to free speech on the Internet –– and likely a first step towards much broader online censorship. Please help us fight back: The first step is signing our petition. We'll give you the tools to share it with your friends and call your Senator.