Opposition

A contentious proceeding before the European Patent Office (EPO) initiated by a third party ("the opponent") following the grant of a European Patent to seek the revocation of that patent. 

An opposition may be initiated by a third party at any point during a 9-month period following the grant of a European Patent. It involves a series of written submissions in which the opponent sets out their arguments and accompanying evidence as to why the patent is invalid and the owner (or "proprietor") of the patent responds to those arguments and/or requests amendments to the claims of their patent which address the issues raised.  The proceeding will usually conclude with an oral hearing attended by both parties (referred to as "Oral Proceedings") held before an impartial panel at the EPO (referred to as the "Opposition Division").  At the end of the hearing, the Opposition Division will issue a decision to either: maintain the patent; maintain the patent in an amended form; or revoke the patent.  This decision can be appealed.