§ 5. Militia call by the United States. When the militia of the state is called forth under the constitution and laws of the United States, the governor shall order out for service the organized militia or such part thereof as may be necessary, and if the number available be insufficient, the governor may call for and accept from the unorganized militia as many volunteers as are required for service in the organized militia or he may direct the members of the unorganized militia or such of them as may be necessary to be drafted into the organized militia.