An offense committed by a member of the national guard shall be tried in civil courts and prosecuted by civil authorities except offenses of a purely military nature. This policy shall be executed and carried into effect at all times and applies to all encampments, armory drill periods and parade periods in addition to any duty performed by the militia under sections 366, 601 and 602 of this title. (Amended 1973, No. 223 (Adj. Sess.), § 11, eff. April 4, 1974.)