As I mentioned in this post last week, in many countries, including the U.K., Germany, China, and Japan, anyone can initiate an action to invalidate a patent. (I'm not talking here about oppositions, but rather about nullification or invalidation actions which can be commenced after the time for filing an opposition has passed.) As I also discussed, U.S. practice is more restrictive, though not quite as restrictive as it was prior to the Supreme Court's 2007 decision in MedImmune.
French law lies somewhere in between these two models, as I discuss in my book at p.278 n.220. A person may file an action to invalidate a patent if he can demonstrate that the patent is capable of harming him, by reason of either his actual or potential activities. A recent case on point--too recent to make its way into my book--is Sebban v. Barilla France, Cour d'appel de Paris, Mar. 6, 2013, PIBD No. 983, III 1150. Barila sought to invalidate two patents owned by Alain and Claude Sebban. The court of first instance held that Barila had standing and declared one claim of each patent invalid for lack of novelty. The Court of Appeals reversed, stating inter alia that a nullification action may be brought by any person having a direct and personal interest in proceeding (intérêt à agir) in the sense of article 31 of the Code of Civil Procedure; that a competitor may proceed if it has an interest in freeing up a use similar to that of the patented technique; that Barila neither established nor alleged the existence of preparatory acts or serious projects for implementing a technique close to that of the challenged patents; and that the patentees had never invoked an identity, real or supposed, between the patented invention and the object exploited by Barila. The case report in PIBD also includes an editor's note on other cases discussing what sort of an interest suffices, including the Omnipharm case that is mentioned in my book.