Opposition can be filed against a granted French patent within 9 months from publication of mention of grant in the French patent bulletin.
Opposition proceedings contain 4 phases:
- an information phase wherein the patentee is informed of the opposition and is given a delay to file observations and/or amendments
- an investigation phase wherein the French patent office issues an opinion and allows parties to file observation within a given delay
- a written phase wherein parties can file written observations, and also amendments for the patentee
- possibly an oral phase to allow parties to present their arguments during a hearing.
Decree can be found <link https: www.legifrance.gouv.fr external-link-new-window internal link in current>here.