From the Housing and Community Development Act of 1992 that established the authority of HUD to set affordable housing goals for Fannie and Freddie (along with a zillion other attempts  to manipulate the housing market)
Enterprises Financial Safety and Soundness Act of 1992 – Sets forth
congressional findings and definitions. Declares that this Act and the
amendments it makes may not be construed: (1) as obligating the Federal
Government, either directly or indirectly, to provide any funds to the
Federal Home Loan Mortgage Corporation (Freddie Mac), the Federal
National Mortgage Association (Fannie Mae), or the Federal Home Loan
Banks, or to honor, reimburse, or otherwise guarantee any of their
obligations or liabilities; or (2) as implying that any such enterprise
or Bank, or any obligations or securities of such an enterprise or
Bank, are backed by the full faith and credit of the United States.
Good thing they got that straight.