There were slaves in mainland France (especially in trade ports such as Nantes or Bordeaux)., but the institution was never officially authorized there. The legal case of Jean Boucaux in 1739 clarified the unclear legal position of possible slaves in France, and was followed by laws that established registers for slaves in mainland France, who were limited to a three-year stay, for visits or learning a trade. Unregistered "slaves" in France were regarded as free. However, slavery was of vital importance to the economy of France's Caribbean possessions, especially Saint-Domingue.