42 U.S.C. § 1715

The action of the Secretary in allowing or denying any payment under subchapter I shall be final and conclusive on all questions of law and fact and not subject to review by any other official of the United States or by any court by mandamus or otherwise, and the Comptroller General is authorized and directed to allow credit in the accounts of any certifying or disbursing officer for payments in accordance with such action.