No Govt guarantee on MBSs, but a UST backup of FnF in the Charter Act, regarding the purchase of redeemable obligations at a rate similar to Treasuries, such as SPS: "obligations in regard of Capital Stock" (quote from the SPSPA)
In exchange for their risky Public Mission "purposes".
Statutory provision: "Authority of Treasury to Purchase Obligations". Subsection (c). Redeemable obligations. Subsection (b)
The credit losses are borne by the regulatory capital in FnF.
It isn't an insurance against losses, FHA- or FDIC- style. The Govt never bears credit losses. You are here to mislead the public.
The UST is prohibited to get compensated for this backup while there is no actual investment. Subsection: "PROHIBITION".
This is what is explicitly stated in the law. "Implied" or "implicit" Govt Guarantee on MBSs, is used by the scammers.