Except as otherwise provided in subsection 4 of NRS 616B.627, when the State or a county, city, school district, metropolitan police department, or other political subdivision, or a contractor under such a governmental entity is the employer, the provisions of chapters 616A to 616D, inclusive, of NRS for the payment of compensation and the amount thereof for any injury sustained by an employee are conclusive, compulsory and obligatory upon both employer and employee without regard to the number of persons in the service of any such employer.