Jurisdiction — In general — Territorial — Territorial limits of jurisdiction — Patents — Measures requested from French courts to assist in enforcing Belgian decision concerning infringement of Belgian patent of Belgian company by French firm — French patent of Belgian company cancelled — Principle of territoriality of patents — Union of Paris for the Protection of Industrial Property (Article 2) — National treatment — Inapplicability in respect of cancelled patent — Whether Belgian decisions in patent proceedings may be granted exequatur — Whether contrary to ordre public — Whether investigations in France to verify compliance with Belgian injunction may be ordered by French courts — The law of France