N.H. Rev. Stat. § 106-N:9
In order to more effectively carry out the purposes of this chapter, the governor of this state, referred to as the empowering state, may enter into a reciprocal agreement with the governor of any other state, referred to as the reciprocal state, subject to any regulations prescribed under such agreement, empowering a railroad police officer with the right to perform any police function that can be lawfully exercised by a police officer of the reciprocal state relating to the detection and apprehension of any person committing an offense against the empowering or the reciprocal state, but only to the extent that such offense is committed on property owned, operated or maintained by the appointing railroad or committed against property owned or in the possession of such railroad.
RSA 106-N:9
1979, 331:1, eff. Aug. 21, 1979.