N.H. Rev. Stat. Ann. § 644:8-b

If any person shall cut the bone of the tail of a horse for the purpose of docking the tail, or shall cause or knowingly permit the same to be done upon the premises of which he is in control, or shall assist in or be present at such cutting, he shall be guilty of a misdemeanor. Written permission from the state veterinarian shall be obtained by a licensed veterinarian to perform surgical operations pursuant to this section. The state veterinarian shall promulgate rules relative to granting authorization for such operation.