N.H. Rev. Stat. § 649:8
Any peace officer or any person employed as watchman, guard, or in a supervisory capacity on premises posted as provided in RSA649:7 may stop any person found on any premises to which entry without permission is forbidden by said section and may detain him for the purpose of demanding, and may demand, of him his name, address and business in such place. If said peace officer or employee has reason to believe from the answers of the person so interrogated that such person has no right to be in such place, said peace officer shall forthwith release such person or he may arrest such person without a warrant on the charge of violating the provisions of RSA649:7; and said employee shall forthwith release such person or turn him over to a peace officer, who may arrest him without a warrant on the charge of violating the provisions of said section.
RSA 649:8
1971, 518:1, eff. Nov. 1, 1973.