N.H. Rev. Stat. Ann. § 547:13

He shall not act as counsel or advocate in any business in, or which may be brought into any probate court. No attorney shall be permitted to practice before any probate judge who is a partner, associate, employee or employer of said attorney, or is a stockholder in a professional corporation for the practice of law in which said attorney is stockholder. Full-time probate judges under RSA 547:2-a shall be prohibited from the practice of law to any degree.