A federal judge on Wednesday upheld a U.S. Securities and Exchange Commission rule that will require about 6,000 publicly traded companies to report whether their products contain four so-called conflict minerals from the Democratic Republic of the Congo, where warlords use proceeds from the mineral sales to finance murder, rape and torture.

The National Association of Manufacturers, the U.S. Chamber of Commerce and the Business Roundtable sued the SEC to block the rule, which they said might cost as much as $16 billion to implement. They argued that the disclosure requirement was arbitrary and capricious and violated companies’ First Amendment rights.