American law, with its strong First Amendment traditions, makes it hard to sue authors for libel. To get around these protections, book subjects have been suing American authors in England, where the libel law is much less writer-friendly. Two states – New York and Illinois – have already adopted laws prohibiting “libel tourism,” and several more, including Florida and California, may soon join them.

That is a good start, but it still leaves writers with only a patchwork of protection. Congress needs to pass a law that makes clear that no American court will enforce libel judgments from countries that provide less protection for the written word.

The dangers to authors and free speech are clear in the case of Rachel Ehrenfeld, who wrote a book in 2003 alleging that a prominent Saudi businessman financed terrorism. The book was published in the United States, but because a few copies were sold over the Internet in England, the British courts allowed the businessman to sue for libel.

In British law, writers are at a distinct disadvantage. In some cases, the burden is on them to prove the truth of what they have written, rather than on the subject to prove that it was false. Ms. Ehrenfeld decided not to defend herself because she did not believe she should have to appear before a British court. The Saudi businessman was awarded more than $200,000 in damages.

The House of Representatives passed a bill against libel tourism last year. Peter King, Republican of New York, and Anthony Weiner, Democrat of New York, are sponsoring a stronger bill, which would, among other things, allow writers in Ms. Ehrenfeld’s position to countersue for treble damages. Congress should pass one of these versions of the law, preferably the tougher one, which has a companion bill in the Senate.

If authors believe they are too vulnerable, they may be discouraged from taking on difficult and important topics, like terrorism financing, or from writing about wealthy and litigious people. That would not only be bad for writers, it would be bad for everyone.