In the United States, the practice of law is conditioned upon admission to practice of law, and specifically admission to the bar of a particular state or other territorial jurisdiction. The American Bar Association and the American Law Institute are among the organizations that are concerned with the interests of lawyers as a profession and the promulgation of uniform standards of professionalism and ethics, but regulation of the practice of law is left to the individual states, and their definitions vary.
The definition of "unauthorized practice of law" is variable, and is often conclusory and tautological, i.e., it is the doing of a lawyer's or counselor's work by a non-lawyer for money. There is some agreement that appearing in a legally constituted court in a legal proceeding to represent clients (particularly for a fee) is considered to be unauthorized practice of law. But other variations are subject to interpretation and conflicting regulation, particularly as to the scope and breadth of the prohibition. Black's Law Dictionary defines unauthorized practice of law as "The practice of law by a person, typically a nonlawyer, who has not been licensed or admitted to practice law in a given jurisdiction."
The Restatement (Third) of the Law Governing Lawyers notes:
The definitions and tests employed by courts to delineate unauthorized practice by non-lawyers have been vague or conclusory, while jurisdictions have differed significantly in describing what constitutes unauthorized practice in particular areas.