For Social Security coverage purposes under section 218 of the Act, interstate instrumentalities are treated, to the extent practicable, as States, that is:
They must be legally authorized to enter into an agreement with the Commissioner;
They are subject to the same rules that are applied to the States;
They may divide retirement systems and cover only the positions of members who want coverage; and
They may provide coverage for firefighters and police officers in positions under a retirement system.