Mo. Rev. Stat. § 27.040

When required, he shall give his opinion, in writing, without fee, to the general assembly, or to either house, and to the governor, secretary of state, auditor, treasurer, commissioner of education, grain warehouse commissioner, director of the department of commerce and insurance, the director of the division of finance, and the head of any state department, or any circuit or prosecuting attorney upon any question of law relative to their respective offices or the discharge of their duties.