under the law of the European Union a person has the right to continue his vocation or profession in another member state as a self-employed person rather than as a worker. He may be able to provide services there, but that falls under the free movement of services. The rules apply to firms and companies as well as individuals. The greatest difficulty is with the liberal professions, and great activity has gone into the issues of mutual recognition of diplomas: see Reyners v. Belgium [1974] ECR 631.
Collins dictionary of law. W. J. Stewart. 2001.