Each unit of the North Dakota national guard, upon approval of the adjutant general, is authorized to maintain a nonreverting unit fund for purposes as prescribed by federal law and regulations relating to unit funds of the federal military forces and to pay petty operating, equipment, and supply costs incurred by the individual units. All funds transferred by the adjutant general to the unit fund must be deposited in the unit fund and are hereby appropriated for the maintenance and operation of the unit funds. Unit funds may be expended upon authorization of the unit fund custodian designated by the adjutant general under guidelines established by the adjutant general.