In New Hampshire, who can act against someone practising law without a licence?
Answered for: New Hampshire
311:7-a Petition for Injunction. – I. Upon the attorney general's own information or upon complaint of any person, including any judge or any organized bar association in this state, the attorney general may maintain an action for injunctive relief in the supreme or superior court against any person who renders, offers to render, or holds himself or herself out as rendering any service which constitutes the unauthorized practice of the law.
The New Hampshire section lets the attorney general seek an injunction, on their own information or on anyone's complaint. It reaches rendering the service, offering to render it, and holding oneself out as rendering it.
This answer is true in New Hampshire and nowhere else on this site. Another jurisdiction is another answer, or an honest gap: see what has been read for New Hampshire.