Federal Court Upholds Decision on Ambiguous Patent Claims
📌 In brief
In a recent decision, the Federal Court of Appeal upheld the ruling that certain patent claims were invalid because they were too ambiguous. The court emphasized the importance of clear definitions in patent claims to ensure they provide adequate notice to the public.
⚖️ Legal holding
Patent claims must be unambiguous to be valid.
📖 Technical summary
The Federal Court of Appeal upheld the decision that the patent claims were invalid due to ambiguity.
📜 Headnote Official document
The Federal Court of Appeal upheld the decision that patent claims were invalid due to ambiguity, emphasizing the need for clear definitions in patent claims to ensure they serve their notice function.
📚 Full judgment Official document
Date: 20260122 Docket: A-274-24 Citation: 2026 FCA 13 CORAM: [NAME] J.A. ROUSSEL J.A. GOYETTE J.A. BETWEEN: [COMPANY]. Appellant and [COMPANY]. Respondent Heard at Montréal, Quebec, on January 22, 2026. Judgment delivered from the Bench at Montréal, Quebec, on January 22, 2026.
REASONS FOR
JUDGMENT OF THE COURT BY: [NAME] J.A. Date: 20260122 Docket: A-274-24 Citation: 2026 FCA 13 CORAM: [NAME] J.A. ROUSSEL J.A. GOYETTE J.A. BETWEEN: [COMPANY]. Appellant and [COMPANY]. Respondent
REASONS FOR
JUDGMENT OF THE COURT (Delivered from the Bench at Montréal, Quebec, on January 22, 2026). [NAME] J.A. [ 1 ] This appeal concerns a decision by the Federal Court (2024 FC 871, per Justice Nicholas McHaffie) addressing allegations of infringement and invalidity of a pair of related patents that describe metal powder atomization manufacturing processes used to produce high quality powders useful for applications such as 3D printing, powder injection molding, hot isostatic pressing and [COMPANY]: Canadian Patents Nos. 3,003,502 (the 502 Patent) and 3,051,236 (the 236 Patent). Of particular importance to this appeal, the Federal Court found that the term “depletion layer” in the claims in issue was not a term of art and that the skilled reader of the patents in suit would not be able to construe this term. On this basis, the Federal Court found the claims in issue to be invalid for ambiguity. [ 2 ] The appellant, [COMPANY]. ([NAME]), argues that the Federal Court erred in effectively requiring that a valid (unambiguous) patent claim include means of proving infringement. Having carefully reviewed the decision under appeal and having considered [NAME]’s written and oral submissions, it is our view that the Federal Court made no such error. [ 3 ] The Federal Court was correct to observe at paragraph 325 of its reasons that the claims of a patent must define distinctly and in explicit terms the subject matter of the invention for which an exclusive privilege or property is claimed (subsection 27(4) of the Patent Act , R.S.C. 1985, c. P-4), and that failure to do so may render the patent invalid for ambiguity. The Federal Court was also correct to state at paragraph 328 of its reasons that the scope of a patent’s prohibition should be made clear so that members of the public may know where they can go with impunity, and that when the claims, read purposively in the context of the patent as a whole, and with a mind willing to understand, do not permit the skilled reader to understand what falls within the claim and what does not, the patent does not serve its notice function and becomes a “patent of uncertain scope” that is a “public nuisance” ( Free World Trust v. Électro [COMPANY]. , 2000 SCC 66, [2000] 2 S.C.R. 1024 at paras. 41 and 42). The Federal Court was also fully aware of the general disinclination of the courts to find a patent claim invalid for ambiguity. The Federal Court did not misstate the law on ambiguity. [ 4 ] After a thorough review of the patents in suit, the evidence, the applicable law and the parties’ submissions, the Federal Court concluded that the claims in issue were ambiguous because the skilled reader would not be able, as regards the 502 Patent, to distinguish between the depletion layer and the native oxide layer, and hence would not be able to determine whether the former was deeper and thicker than the latter, and as regards the 236 Patent, to determine the existence of a depletion layer or its parameters. [ 5 ] In these conclusions, we see no error of law, no palpable and overriding error of fact, nor any error of mixed fact and law from which an error of law is extricable. The Federal Court explained its reasoning throughout and took proper account of the evidence before it. The Federal Court was entitled to reach the conclusions it did. The Federal Court also properly recognized the differences in the wording of the various claims of the patents in suit. [ 6 ] We do not accept [NAME]’s argument that the Federal Court could not properly conclude that the claims in issue were ambiguous because it was able to construe them. The Federal Court stated clearly that the claims in issue provided insufficient definition to understand their scope. [ 7 ] In view of our conclusion on the issue of ambiguity, it is not necessary to consider [NAME]’s arguments on the issues of insufficiency and infringement. [ 8 ] We will dismiss the present appeal with costs fixed in the all-inclusive amount of $30,000. "[NAME]" J.A. FEDERAL COURT OF APPEAL NAMES OF COUNSEL AND SOLICITORS OF RECORD DOCKET: A-274-24 STYLE OF CAUSE: [COMPANY]. v. [COMPANY]. PLACE OF HEARING: MONTRÉAL, QUEBEC DATE OF HEARING: January 22, 2026
REASONS FOR
JUDGMENT OF THE COURT BY: [NAME] J.A. ROUSSEL J.A. GOYETTE J.A. DELIVERED FROM THE BENCH BY: [NAME] J.A. APPEARANCES : [NAME] For The Appellant [NAME] For The Respondent SOLICITORS OF RECORD : [COMPANY], Ontario For The Appellant [COMPANY] Montréal, Quebec For The Respondent
⚖️ What tends to weigh in cases like this
✅ Tends to be accepted
- The Federal Court correctly stated that patent claims must distinctly define the invention's subject matter.
- The Federal Court was right to say that a patent's scope should be clear so the public knows what is prohibited.
- The Federal Court correctly concluded that the claims were ambiguous because a skilled reader could not distinguish between layers in the 502 Patent.
- The Federal Court correctly concluded that the claims were ambiguous because a skilled reader could not determine the existence or parameters of a depletion layer in the 236 Patent.
- The Federal Court's reasoning was explained throughout and properly considered the evidence.
❌ Tends to be rejected
- The appellant's argument that the Federal Court wrongly required proof of infringement for a valid claim was rejected.
- The appellant's argument that the Federal Court could not find claims ambiguous because it was able to construe them was not accepted.
Patterns observed in similar cases in this collection — every case is unique.
❓ Frequently asked questions
What did this decision decide?
The Federal Court of Appeal upheld the decision that the patent claims were invalid due to ambiguity.
What was the dispute about?
The dispute was over whether the patent claims were clear enough to be legally valid.
How did the court decide, and why?
The court decided that the patent claims were invalid because they were ambiguous, meaning they did not clearly define the subject matter of the invention.
Which laws or rules were applied?
The Patent Act, specifically section 27(4), was applied.
What was the argument that mattered most?
The argument that mattered most was that the patent claims were ambiguous and thus invalid.
Was the decision for or against the person who brought the case?
The decision was against the person who brought the case, as the patent claims were found to be invalid.
What does this mean for someone in a similar situation?
Someone in a similar situation should ensure that their patent claims are clear and unambiguous to avoid being invalidated.
What evidence or documents mattered?
The judgment does not specify the exact evidence or documents that mattered.