12 C.F.R. § 701.20
Suretyship and guaranty
(a) Scope. This section authorizes a federal credit union to enter into a suretyship or guaranty agreement as an incidental powers activity. This section does not apply to the guaranty of public deposits or the assumption of liability for member accounts.
(b) Definitions. A suretyship binds a federal credit union with its principal to pay or perform an obligation to a third person. Under a guaranty agreement, a federal credit union agrees to satisfy the obligation of the principal only if the principal fails to pay or perform. The principal is the person primarily liable, for whose performance of his obligation the surety or guarantor has become bound.
(c) Requirements. The suretyship or guaranty agreement must be for the benefit of a principal that is a member and is subject to the following conditions:
(1) The federal credit union limits its obligations under the agreement to a fixed dollar amount and a specified duration and
(2) The federal credit union's performance under the agreement creates an authorized loan that complies with the applicable lending regulations, including the limitations on loans to one member or associated members or officials for purposes of §§ 701.21(c)(5), (d); 723.4(c).