Patent Re-Examination Board Decision Does Not Preclude Patent Validity Challenge in Court

On May 20th, 2025, the Ontario Superior Court of Justice in Zacon Limited v. Provincial Doors Inc., 2025 ONSC 2954 found that the validity of a patent may be challenged in court on the same grounds previously rejected by a Canadian Patent Office Re-examination Board. This decision confirms that the Court has exclusive jurisdiction to hear and decide patent “validity”  challenges. Re-examination decisions by the Canadian Intellectual Property Office (CIPO) do not disturb this jurisdiction.

Background

The Canadian Patent Act does not offer a robust post-grant patent challenge mechanism before CIPO, unlike, for example, the Inter partes review procedure in the United States. Instead, parties have the ability to seek re-examination of a granted patent. At a high level, a party seeking re-examination can submit prior art to CIPO that was not considered during prosecution. CIPO can then consider whether a “substantial new question of patentability” arises from the prior art, and if so, determine whether the prior art renders the granted claims obvious or anticipated. 

In this case, the plaintiff and patent holder, Zacon, moved to strike portions of the defendant’s statement of defence which alleged the patent to be invalid on the grounds of anticipation and obviousness. The defendant had previously raised the very same allegations in a re-examination proceeding, which CIPO denied.  Zacon argued that it was an abuse of process for the defendant to re-raise the same arguments in a patent action. The Court disagreed.

Decision

In forceful reasons, the Court found there was no abuse of process. The Court held that the Patent Act draws a distinction between “patentability” and patent “validity”. The former is determined by CIPO through the examination and any re-examination process. However, the Court found validity is to be determined only by the court” for the following reasons:[1]

• First, the examination and re-examination processes are directed specifically towards the issue of patentability not patent validity.
• Second, the Patent Act specifically reserves the issue of validity of an issued patent to the courts.  Section  59 provides that the defendant in an action for infringement of a patent may plead as matter of defence any fact or default which by the Patent Act or by law renders the patent void, and section 60 provides that any interested person may seek a declaration that a patent is void, by way of action in the Federal Court.
• Third, section 53.1 of the Patent Act provides that in any action respecting a patent, a written communication may be admitted into evidence to rebut any representation made by the patentee in the action as to the construction of a claim in the patent if it is prepared in respect of, among other things, a request for re-examination or a re-examination proceeding. Thus, notwithstanding a request for re-examination, the validity of a patent may subsequently be put in issue before the court.
• Fourth, section 42 of the Patent Act provides that a patent gives the patentee the exclusive rights to the invention “subject to adjudication in respect thereof before any court of competent jurisdiction”. This section infers that disputes with respect to validity are to be determined by the court.
• Fifth, section 43(2) of the Patent Act provides that after a patent is issued, it shall, in the absence of any evidence to the contrary, be valid. Again, the inference is that findings of invalidity are the role of the court.

[1] See para 23.