N.H. Rev. Stat. § 649:7
Any individual, partnership, association, corporation, municipal corporation or state or any political subdivision thereof engaged in, or preparing to engage in, the manufacture, transportation or storage of any product to be used in the preparation of the United States or of any of the states for defense or for war or in the prosecution of war by the United States, or by any country with which the United States shall then maintain friendly relations, or the manufacture, transportation, distribution or storage of gas, oil, coal, electricity or water, or any of said natural or artificial persons operating any public utility, whose property, except where it fronts on water or where there are entrances for railway cars, vehicles, persons or things, is surrounded by a fence or wall, or a fence or wall and buildings, may post around his or its property at each gate, entrance, dock or railway entrance and every 100 feet of water front a sign reading "No Entry Without Permission." Whoever without permission of such owner shall wilfully enter upon premises so posted shall be guilty of a misdemeanor.
RSA 649:7
1971, 518:1, eff. Nov. 1, 1973.