N.H. Rev. Stat. Ann. § 438:18

The commissioner shall have concurrent authority to enforce the provisions of this chapter, in cities for which sealers of weights and measures have been appointed as provided in this chapter. City sealers shall investigate and prosecute within the jurisdiction of the city, unless the investigation or prosecution in the jurisdiction over a particular case or class of cases is preempted by the state bureau of weights and measures, county attorney or attorney general. City sealers, upon request of the bureau of weights and measures, county attorney, or attorney general, may assist and conduct investigations throughout the state.