N.H. Rev. Stat. § 106-I:1
Notwithstanding any law to the contrary, a law enforcement officer who responds to a mass critical incident in another jurisdiction, in response to a request by the highest ranking on-duty police officer of the requesting jurisdiction, shall have authority to make arrests and shall have full police powers for the duration of the incident, unless terminated by the law enforcement authority in the requesting jurisdiction. The request for assistance must be received directly from the highest ranking officer or indirectly through a law enforcement dispatch center. For purposes of this section, a mass critical incident includes such events as a natural disaster, riot, hazardous material incident, an act of terrorism, or widespread personal injury or loss of life.
RSA 106-I:1
2003, 252:1, eff. July 14, 2003.