N.H. Rev. Stat. Ann. § 215-A:4

The use of any frozen surface of any public body of water by the owner or operator of any OHRV, shall be done at their own risk; and any accident resulting shall not be a legal responsibility of any town, city, or the state. The executive director may, in the interest of public safety, close temporarily to any motorized vehicle all or any part of any frozen surface of a public body of water, for use by the public, except for fishing on foot.