Our nation has also long understood that copyright law, while adopted to promote creative arts, similarly raises potential threats to freedom of speech. For example, if you use someone else's words against them while criticizing a book or corporate actions, you could expect a copyright suit intended to suppress your criticism. The Supreme Court has crafted doctrines such as "fair use," which permits copying materials for criticism, parody, and transformative uses, and has ruled that abstract ideas are not subject to copyright, because courts will not punish people for merely using an abstract concept in speech.

In the 1990s, Congress heeded both these lessons and adopted laws translating these long-standing constitutional concerns to the Internet. Knowing that defamation or copyright suits could cripple the emerging speech platforms, legislators provided immunities -- or safe harbors -- for sites following specific procedures. Congress created a safe harbor for defamation in 1996 and for copyright in 1998. Both safe harbors were designed to ensure that the Internet would remain a participatory medium of speech. After all, if AOL were responsible for every defamatory comment responding to chat-room chatter or news clips, or for every copyright infringement on its instant messaging system, it would either have had to shut down or to assert control over all the speech on its platforms.

Other companies would have faced the same choice, and many sites that have launched since then, such as Blogger and Facebook, might have lacked the legal protections to launch. These safe harbors, in their way, helped preserve the Internet's potential for participatory, many-to-many communications unimaginable in the pre-1990s era dominated by one-to-many television and newspapers.

But since then, Congress has become inconsistent in its sensitivity to free speech threats. Lawmakers deserve credit for continuing to guard against defamation's burden. In 2010, Congress passed the SPEECH Act, forbidding American courts from enforcing certain foreign defamation judgments. Plaintiffs had been bringing defamation claims against Americans in countries halfway around the world where plaintiffs were more likely to prevail and where free-speech considerations did not limit defamation cases. This "defamation tourism" could stifle robust American debate online. In the words of bill supporter Sen. Patrick Leahy, a longtime civil liberties advocate, the "chilling" potential of these defamation actions threatened the "freedoms of speech and the press" that are "cornerstones of our democracy."

Today, however, Congress is considering passing major legislation to change the definitions of online infringement. While supposedly aimed at foreign "rogue sites" like the Pirate Bay in Sweden, the legislation's new definitions would alter the copyright safe-harbor and make platforms for user-generated speech -- including Twitter, Facebook, and YouTube -- liable for copyright infringement committed by users. These sites would have to adopt Big Brother technologies to monitor all their users' activities in order to make sure no user is sharing the latest release from the Twilight series.