The lives of a group of individuals may be insured under a policy issued to the commanding officer, which commanding officer shall be deemed the policyholder, to insure not less than twenty-five of the members of the Washington state patrol. Such policy shall be for the benefit of beneficiaries as designated by the individuals so insured, and the premium thereon may be paid by such members. Not less than seventy-five percent of all eligible members of such Washington state patrol, or of any unit thereof determined by conditions pertaining to their employment, may be so insured.