N.H. Rev. Stat. Ann. § 627:7

A person in possession or control of premises or a person who is licensed or privileged to be thereon is justified in using non-deadly force upon another when and to the extent that he reasonably believes it necessary to prevent or terminate the commission of a criminal trespass by such other in or upon such premises, but he may use deadly force under such circumstances only in defense of a person as prescribed in RSA 627:4 or when he reasonably believes it necessary to prevent an attempt by the trespasser to commit arson.