This is the last part of the "Stay in Mexico" policy which is Title 42.
Grant funding actions. Under section 402(j)(5)(A) of the Public Health Service Act (42 U.S.C. 282(j)(5)(A)), if an applicable clinical trial is funded in whole or part by the Department of Health and Human Services, any required grant or progress report forms must include a certification that the responsible party has made all required registration and results submissions. If it is not verified that the required registration and results clinical trial information for each applicable clinical trial for which a grantee is the responsible party has been submitted, any remaining funding for a grant or funding for a future grant to such grantee will not be released. If the head of an HHS agency verifies that a grantee has not submitted such required clinical trial information, the agency head will provide notice to the grantee of the non-compliance and allow the grantee 30 days to correct the non-compliance and submit the required clinical trial information
https://www.ecfr.gov/current/title-42/chapter-I/subchapter-A