Missouri Revised Statutes Title XXI. Public Safety and Morals § 321.223. Fire protection districts may contract to provide fire protection to municipalities not in the district, certain counties (including St. Louis County)--may also provide ambulance service, when

1. Notwithstanding any other provision of law to the contrary, any fire protection district within a county of the first classification with a charter form of government with a population of at least nine hundred thousand may contract with any municipality or village that does not operate its  1 own fire department to provide fire protection services for a fee to any area of the municipality or village that does not belong to the fire protection district. In such event, the municipality and the fire protection district shall, by ordinance duly enacted by the governing board of each, agree upon the terms by  2 which such fire protection shall be furnished. The agreement may provide for the payment of a stated sum per year upon any method of compensation for such fire protection that is agreed upon by the fire district and the municipality entering into such contract; provided that any contract for a period longer than five years shall have no binding force until ratified by a majority of the voters in the fire district and the municipality entering into such a contract.

2. If the fire protection district is authorized to provide ambulance service within its district, the fire protection district may also provide ambulance service to the municipality, upon such terms as the fire district and the municipality may agree, which are not inconsistent with any requirement of subsection 1 of this section.