Neb. Rev. Stat. §§ 55-135
The number and grade of officers and enlisted personnel shall be as prescribed by the United States Department of the Army and the Department of the Air Force personnel documents provided to the National Guard or as otherwise authorized, but in case of war, invasion, insurrection, riot, or imminent danger, the Governor may temporarily increase them to meet such emergencies. All officers shall hold their commissions until separated by reason of resignation, disability, or pursuant to applicable regulations issued by the Department of the Army or the Department of the Air Force. Vacancies among officers shall be filled by appointment, subject to such regulations relating thereto as now or may hereafter be promulgated by the United States Government.
Neb. Rev. Stat. §§ 55-135