A federal appeals court on Wednesday refused to stay the U.S. Securities and Exchange Commission’s conflict-minerals rule, dashing the hopes of companies seeking to avoid compliance with the costly regulation.

In a one-sentence order, the U.S. Court of Appeals for the D.C. Circuit denied an emergency motion by the National Association of Manufacturers and other business groups to delay the rule, which requires about 6,000 publicly traded companies to document the source of all gold, tin, tantalum and tungsten used in their products. Without a stay, companies must file their first reports with the SEC by June 2.