Re-Examination Of Patentability Does Not Preclude Subsequent Claims For Patent Invalidity Says Ontario Court

On May 20, 2025, the Ontario Superior Court of Justice (the Court) issued its decision in Zacon Limited v Provincial Doors Inc., 2025 ONSC 2954, dismissing Zacon Limited’s (the Plaintiff’s) motion to strike the defences asserted by Provincial Doors Inc. and Pretium Resources Inc. (collectively, the Defendants) on the grounds that they were previously considered in a final decision of a Patent Re-examination Board and would be an abuse of process.  

The Plaintiff initiated a patent infringement action against the Defendants for Canadian Patent No.  2,348,348 (the 348 Patent). In response, the Defendants argued, among other things, that the 348 Patent was invalid due to anticipation and obviousness. Separately, a representative of Provincial Doors Inc. also sought a re-examination of the 348 Patent by a Re-Examination Board (the Board) on similar grounds (i.e., certain documents anticipated the 348 Patent and/or rendered it obvious). However, the Board decided that the provided documents did not raise a new question of patentability and denied the request. The Board’s decision was considered final with no right of appeal.

The Plaintiff took the position that the defences asserted by the Defendants in the patent infringement action were identical to the allegations in the request for re-examination by the Board and, therefore, it would be an abuse of process for the Court to allow duplicative proceedings and a de facto review of the Board’s final decision.

In reviewing the matter, the Court held that the questions to be decided by the Board on re-examination are not the same as the questions decided by the Court for a claim of invalidity. A request for re-examination considers “patentability”, where the Board assesses if new information impacts upon whether a patent ought to have been issued in the first place. In contrast, the Court was asked to determine the 348 Patent’s “validity”, which reviews the facts or defaults asserted by the Defendants to render the patent void. The Patent Act provides that the determination of patent validity is within the sole purview of the court, so the Defendants’ defences cannot be barred by a re-examination request.

This ultimately led the Court to dismiss the Plaintiff’s motion to strike.

Summary By: Amy Ariganello