The law says only U.S. citizens and U.S.-incorporated companies can hold mining claims on federal land. A new GAO report says the agency in charge rarely checks. In a sample of 15 business claimants, GAO couldn't find evidence that 7 were U.S. companies. A companion report found 14 of 32 companies behind critical mineral mines were subsidiaries of foreign firms, and in at least two cases Chinese entities had a stake in the parent company.