Is Congress about to limit freedom of speech on the Internet? Two bills wending their way through the Senate and the House may do just that.

The proposals, known as the Protect IP Act (PIPA) and the Stop Online Piracy Act (SOPA) are aimed at stopping foreign-based Web sites from distributing copyrighted material, such as Hollywood movies, in violation of U.S. law. Such online “piracy” is a real problem, and since many of the so-called pirate sites distributing content are based off-shore, they have been able to operate without interference.

PIPA and SOPA would try to limit the reach of these pirates by enlisting the help of U.S.-based third parties used in their operation. Most controversially, they would require Internet service providers to block the IP addresses of sites found to be infringing intellectual property rights. This provision, however, has met with a hailstorm of criticism from Internet engineers and others, who argue that such interference with Internet connectivity would have unpredictable effects on the operation of the Web, possibly threatening Internet security. It now looks likely that these provisions will be dropped.

Other provisions, however, also raise concern, among them ones that would prohibit search engines such as Google and Yahoo! from including pirate sites in their search results. In effect, the search engines would be placed under a gag order, prohibiting them from disclosing the location of rogue sites.

This remarkable restriction goes well beyond current law, which requires the “takedown” of content that infringes on intellectual property rights. Under PIPA and SOPA, no portion of a rogue site may be linked—even pages that contain no infringing content.

The constitutionality of this provision is uncertain. Many legal scholars, such as Marvin Ammori of Stanford Law School, argue that this requirement directly violates the First Amendment. Although use of copyrighted content is largely unprotected by the First Amendment, Ammori points out that content merely associated with copyrighted material but is itself not infringing is entitled to traditional First Amendment scrutiny. This includes much content covered by the proposed restriction—for instance, background material on a site otherwise used for infringement.

Under current case law, it is unclear how a court would rule on the constitutionality of the legislation being considered. But whatever the legal argument, the restrictions imposed on search engines by PIPA and SOPA erode freedom of expression on the Web. It’s as if Rand McNally were banned from incidentally including on its maps locations where illegal drug sales are known to occur. (Importantly, the legislation would bar provision of hyperlinks in response to any search query, not just those that specifically request links to illegal content.)

Why should anyone care? After all, few would defend the activities of these pirate sites. But limits on speech here are almost certain to be extended to other cases. If links to pirate sites are banned, why not links to sites disseminating national security secrets? Or sites “facilitating” violence by propagating extreme political positions? Moreover, other countries that have pursued content controls of their own, such as China, may be encouraged by steps in the U.S. to limit content.

Intellectual property rights to content on the Web should be vigorously defended. But not at the expense of the freedom of expression that has made the Internet such a vigorous and dynamic communication tool. The limits being considered by Congress, while well-intended, are a step too far.