THE HOMELAND SECURITY law enacted last year contains a miserable provision that weakens important federal regulation and public access to information. Congress should act soon to repair the damage.

The goal of the provision was reasonable enough: encouraging companies to share information with the government about infrastructure that might be vulnerable to terrorist attack. Fearing public disclosure, companies have been reluctant to share information on vulnerabilities at, say, power plants or chemical factories. So under the law, any such "critical infrastructure" information that companies voluntarily provide to the government is exempted from disclosure to the public, litigants and enforcement agencies.

But the law defines "information" so broadly that it will cover, and thus keep secret, virtually anything a company decides to fork over. A company might preempt environmental regulators by "voluntarily" divulging incriminating material, thereby making it unavailable to anyone else. Unless regulators could show they had obtained the material independently, it would be off limits to them. And the law prescribes criminal penalties for whistle-blowers who make such information public. The collective impact will be to put in the hands of a regulated party the power, simply by turning over information, to shield that information from legitimate law enforcement purposes and from public disclosure. Sens. Patrick J. Leahy (D-Vt.) and Robert F. Bennett (R-Utah) had negotiated a compromise that would accomplish the reasonable purpose without such broad harmful effects. It should be restored before the government finds its hands tied -- and the public finds itself out of the loop -- on important regulatory matters.