Throwback Thursday: CanMar and Foreign File Wrapper Estoppel

Look for Brion Raffoul’s Throwback Thursday posts, where we revisit posts and cases of interest!

In December 2019, we reported on CanMar Foods Ltd. v TA Foods LTD (2019 FC 1233, “CanMar FC”). CanMar FC was the first case to look at Section 53.1 of the Patent Act–a “file wrapper estoppel” provision added to the Act in 2018.

Though long-adopted in the US and the UK, Canada’s courts had explicitly rejected relying on extrinsic evidence, such as prosecution history, when interpreting the scope of Canadian claims (see, e.g., Free World Trust v √Člectro Sant√© Inc., 2000 SCC 66, at para. 66). The introduction of Section 53.1 changed that approach, explicitly permitting the admission of written communications between the applicant / patentee and the Commissioner [or] an officer or employee of the Patent Office “to rebut any representation made by the patentee… as to the construction of a claim in the patent”.

In 2019, in CanMar FC, the Federal Court gave this provision an expansive reading, using it to bring in foreign prosecution history for the purposes of rebutting the patentee’s representation. The Court cited “extraordinary circumstances”: namely, that the patentee “specifically referred to the corresponding US Application prosecution history and acknowledged that the amendments to the claims [in Canada] were made to overcome novelty and obviousness concerns as raised in the US Application prosecution history” (CanMar FC at para. 70).

But this past January, the Federal Court of Appeal ruled that, in this specific circumstance, “the Judge should have refrained from taking into consideration the prosecution history of the corresponding US Application” (2021 FCA 7 at para. 77, emphasis added). The FCA expressed no firm views as to whether Section 53.1 could ever extend to foreign prosecution, but was clear that the limited references to corresponding US prosecution in this Canadian file would not, by themselves, be sufficient.

So, What Does This Mean for Applicants?

Given the FCA’s ruling, general references to foreign prosecution likely will not import those file wrappers into Canada for estoppel purposes. In particular, references to “a corresponding US application” or other foreign application that do not include the foreign serial number will likely not be admissible to rebut the patentee’s claim construction in future. However, the door remains open for other “extraordinary circumstances”–for instance, where foreign prosecution is discussed in detail in written submissions to the CIPO. Applicants would be wise to use caution when tying Canadian amendments to foreign prosecution histories, but need not try to avoid it entirely.

For more information on filing in Canada, contact one of our experts at Brion Raffoul.