20 CFR § 404.1211
Interstate instrumentalities
February 18, 2021
For Social Security coverage purposes under section 218 of the Act, interstate instrumentalities are treated, to the extent practicable, as States, that is:
(a) They must be legally authorized to enter into an agreement with the Commissioner;
(b) They are subject to the same rules that are applied to the States;
(c) They may divide retirement systems and cover only the positions of members who want coverage; and
(d) They may provide coverage for firefighters and police officers in positions under a retirement system.
[53 FR 32976, Aug. 29, 1988, as amended at 61 FR 38368, July 24, 1996; 62 FR 38451, July 18, 1997]