New Hampshire happens to be one of the most tolerant states in the entire United States. There was a prohibition that applies to switchblade knives that got repealed back in 2010. New Hampshire does not have any general prohibitions in regards to carrying, possession or ownership of knives. There is also statewide preemption in New Hampshire. There are also no local or municipal ordinances that could restrict either knife possession or ownership.
New Hampshire Rev. Stat. § 159:26
Ammunition, Firearms, and Knives: Authority Of New Hampshire
I. In regards to the extent that is consistent with federal laws, the state of New Hampshire will have authority as well as jurisdiction of the purchase, sale, use, ownership, possession licensing, transportation, taxation, permitting, or any other matter that pertains to firearms, components of firearms, ammunition, any firearms supplies or knives in the state. With the exception of being specifically provided by the statute itself, no regulation or ordinance of any political subdivision can regulate the sale, ownership, purchase, use, transportation, possession, licensing, taxation, permitting, or any other matter that pertains to the firearms, their components, the ammunition or the firearms supplies in the state. Nothing provided in this section will be construed as having an impact on a political subdivision and their right to adopt any zoning ordinances for the sole purpose of regulating knives or firearms businesses in the same manner as any other businesses or to take any further action allowed under the RSA 207:59.
II. Upon the valid date of this section, any and all municipal regulations and ordinances that are not authorized under paragraph I that is relative to the sale, ownership, purchase, use, possession, licensing, transportation, taxation, permitting or any other matter that pertains to firearms, firearm components, or the ammunition and firearms supplies or knives will be null and void.
New Hampshire does not have any laws in regards to the transfer or sales of knives to minors. However, it does prohibit the sale of bb guns and/or paintball guns to minors.
This information that is presented as a brief description of the laws and not as any kind of legal advice. aStraightArrow.net will not and cannot be a legal service provider. The use of the site does not create any sort of client/lawyer relationship. The knife laws are interpreted differently by prosecuting attorneys, enforcement officers, and judges. aStraightArrow.net suggests you consult legal counsel for further guidance.