Mo. Rev. Stat. § 643.312: Reformulated gasoline program.

The air conservation commission may establish, by rule, a state reformulated gasoline program to prohibit the sale or dispensing of conventional gasoline for use in motor vehicles. If established, such program shall be implemented and reformulated gasoline shall be available at the retail level in the nonattainment area described in section 643.305 by June 1, 1999. The effectiveness of such program in improving air quality shall be at least equal to, and cost competitive with, the federal reformulated gasoline program, 42 U.S.C. 7545. Subject to the conditions of this section, any reformulated gasoline program established pursuant to this section shall not preclude the use of ethanol.