12 CFR § 703.16 - Prohibited investments.
(a) [Reserved]
(b) Stripped mortgage backed securities (SMBS). A Federal credit union may not invest in SMBS or securities that represent interests in SMBS except as described in paragraphs (1) and (3) below.
(1) A Federal credit union may invest in and hold exchangeable collateralized mortgage obligations (exchangeable CMOs) representing beneficial ownership interests in one or more interest-only classes of a CMO (IO CMOs) or principal-only classes of a CMO (PO CMOs), but only if:
(i) At the time of purchase, the ratio of the market price to the remaining principal balance is between .8 and 1.2, meaning that the discount or premium of the market price to par must be less than 20 points;
(ii) The offering circular or other official information available at the time of purchase indicates that the notional principal on each underlying IO CMO should decline at the same rate as the principal on one or more of the underlying non-IO CMOs, and that the principal on each underlying PO CMO should decline at the same rate as the principal, or notional principal, on one or more of the underlying non-PO CMOs; and
(iii) The credit union staff has the expertise dealing with exchangeable CMOs to apply the conditions in paragraphs (e)(1)(i) and (e)(1)(ii) of this section.
(2) A Federal credit union that invests in an exchangeable CMO may exercise the exchange option only if all of the underlying CMOs are permissible investments for that credit union.
(3) A Federal credit union may accept an exchangeable CMO representing beneficial ownership interests in one or more IO CMOs or PO CMOs as an asset associated with an investment repurchase transaction or as collateral in a securities lending transaction. When the exchangeable CMO is associated with one of these two transactions, it need not conform to the conditions in paragraphs (e)(1)(i) and (ii) of this section.
(c) Other prohibited investments. A Federal credit union may not purchase residual interests in collateralized mortgage obligations, real estate mortgage investment conduits, or small business related securities.