No Canadian courts face public international legal issues more often than the Federal Court and the Federal Court of Appeal. In such areas as immigration, taxation, national security, intellectual property and judicial review of federal government action generally, the federal courts regularly confront international legal issues. How international law is received in our law—both substantively and procedurally—is therefore of especial importance to these courts.
Three recent cases—two from the Federal Court and one from the Federal Court of Appeal—have considered the question of whether expert opinion on international legal issues is admissible in evidence. This issue has generated a great deal of inconsistent, and often under-reasoned, Canadian jurisprudence in the last twenty years. But the three cases discussed below suggest we are finally moving in the right direction.
In Boily v. La Reine 2017 FC 396, Prothonotary Morneau struck out an expert report as inadmissible for expressing an opinion about international law as it applied in the case. In doing so he relied in part on a discussion in the second edition of Using International Law in Canadian Courtson the common law distinction between international law (which is a matter of judicial notice) and foreign law (which is not).
Boily appealed the prothonotary’s decision to a judge of the Federal Court: Boily v HMTQ 2017 FC 1021. Justice Gagné upheld the prothonotary’s finding that the report was inadmissible. But rather than affirming the prothonotary’s conclusion that the expert report was excluded by the doctrine of judicial notice of international law, the learned judge preferred to base her reasoning on the fact that the expert report impermissibly opined on questions of law:
 …the state of the law on the admissibility of expertise on international law is uncertain and has received little explicit attention from Canadian courts. What remains far more certain is the inadmissibility of expertise providing legal conclusions on the issue(s) to be decided by the court, whether that law be domestic, foreign or international. Prothonotary Morneau, Mr. Boily and the Crown all agree that pages 10 to 12 of the Report (at least in part) provide an opinion on the relevant international law as it applies to Mr. Boily’s case. This type of legal analysis cannot be the subject of expert evidence and was rightfully deemed inadmissible by Prothonotary Morneau.
On the admissibility of international legal evidence, Gagné J noted that my discussion of the issue was “less definitive that this rule has fully been adopted in Canadian courts” and that while I argued for the orthodox view that international legal questions are questions of law, I also presented “several examples of exceptions to this rule where Canadian judges have accepted expert evidence on international law” (at ). Justice Gagné went so far (at ) as to say that there is “no authoritative legal position in Canada on whether or not judges are to take judicial notice of international law and consequently, on the admissibility of expertise on international law”, and (at ) that there is “clearly no settled position on this point”. Indeed, the prothonotary’s conclusion that “that expert evidence on international law is inadmissible because judges must take judicial notice of international law could be said to be a legal error” and that “[t]hat conclusion is not the law in Canada”. Instead, concluded Gagné J (at ),
Courts’ taking judicial notice of international law and their acceptance of expert evidence on international law will continue to be made on a case-by-case basis going forward, until such point as a Canadian court takes a more definitive stance on this practice.
Had her decision ended there, it would have to be regarded as something of a backwards step. But it did not end there. In fact, Gagné J went on to make statements and findings very much in keeping with the doctrine of judicial notice of international law and the inadmissibility of opinion evidence on international legal questions. She quoted approvingly (at ) the Court of Appeal for British Columbia’s comment in R. v. Appulonappa 2014 BCCA 163 at para. 62 that the experts in that case had “strayed into providing opinions on the interpretation and application of international law and s. 117 of the IRPA”, which testimony was “not properly admissible as these were questions of law for the court”. She also expressly declined to rely on Swinton J’s use of expert evidence in Bouzari v. Iran  OJ No 1624 (Ont SCJ). Gagné J notes trenchantly (but, in my view, fairly) that “the role of the legal experts in [Bouzari] seems to go beyond what Justice Swinton presents their role to be at the beginning of her judgment”, namely to “assist the court in determining the applicable international law” rather than assigning such determinations to the experts themselves. Ultimately, Gagné J held (at ) that “in submitting an expert opinion containing a legal conclusion on international law as it applies to the facts of the case, Mr. Boily submitted inadmissible expert evidence”. Her distance from Prothonotary Morneau’s approach is real, but not great.
As if in response to Gagné J’s observation that Canadian law lacks an authoritative statement of whether or not our judges take judicial notice of international law, Nadon JA for the Federal Court of Appeal went a considerable way to supplying it in Turp v. Canada (Foreign Affairs) 2018 FCA 133. The applicant sought judicial review of the federal government’s decision to sell military vehicles to Saudi Arabia. Both sides relied on expert opinion on the international legal issues. In a discussion entitled, “Proof of international law through expertise”, Nadon JA observed (at ):
I think it is useful to remark, without ruling on the question since the parties have not submitted any argument to this effect, that, in my opinion, the parties do not need to file experts’ reports to prove international law, because the Court can take judicial notice of said law.
The learned judge proceeded to consider The North,Jose Pereira E Hijos, S.A. v. Canada (Attorney General), and Lord Advocate’s Reference, quoting extensively from each:
 In R. v. “North” (The), 1906 CanLII 80 (SCC),  37 S.C.R. 385, 26 C.L.T. 380, one of the questions the Supreme Court of Canada had to decide was whether the Court could take judicial notice of the doctrine of the right to hot pursuit and whether to interpret the relevant legislation in the light of this doctrine. That was an admiralty case about a foreign vessel that had violated Canadian laws on fisheries within the three thousand nautical miles that were, at that time, the territorial limit of Canada and about the right to pursue and seize it on the high seas.
 One of the appellant’s arguments before the Supreme Court was that the admiralty judge, sitting in first instance, had taken judicial notice of the doctrine of hot pursuit and had therefore erred. Justice Davies, with Justice Maclennan concurring, concluded that the admiralty judge had not committed any errors. At page 394, Justice Davies explained the following:
. . . I think the Admiralty Court when exercising its jurisdiction is bound to take notice of the law of nations, and that by that law when a vessel within foreign territory commits an infraction of its laws either for the protection of its fisheries or its revenues or coasts she may be immediately pursued into the open seas beyond the territorial limits and there taken.
. . .
The right of hot pursuit of a vessel found illegally fishing within the territorial waters of another nation being part of the law of nations was properly judicially taken notice of and acted upon by the learned judge in this prosecution.
 More recently, in Jose Pereira E Hijos SA v. Canada (Attorney General), 1996 CanLII 4098 (FC),  2 FC 84, 126 F.T.R. 167, a case concerning the seizure of a Spanish vessel breaking Canadian fisheries laws, Justice MacKay of the Federal Court ruled that it could take judicial notice of international law. More specifically, Justice MacKay had to decide whether the alleged facts mentioned in the plaintiffs’ statement of claim concerning international law should be struck out under Rule 419(1) of the Federal Courts Rules, C.R.C., c. 663. At paragraphs 20 to 22 of his reasons, Justice MacKay stated as follows:
20. The principles concerning the application of international law in our courts are well settled, and they are not here disputed by plaintiffs. One may sum those up in the following terms: accepted principles of customary international law are recognized and are applied in Canadian courts, as part of the domestic lawunless, of course, they are in conflict with domestic law.
. . .
21. The plaintiffs profess to accept those principles governing the relationships of international and domestic law. They do not contest that if there is conflict, the Court will apply domestic law. But they do urge, and seek the opportunity to establish at trial, that the amended Regulations are unlawful for a variety of reasons.
. . .
22. That issue, one fundamental to these proceedings, may be raised without reference in the pleadings or particulars to specific international treaties or conventions which, in so far as they are considered a source of law, will be applied in the action only if they are incorporated in Canadian domestic law by legislation specifically so providing. To the extent that international conventions or treaties are considered authority for international law principles, it is unnecessary to plead them specifically, in the same way that it is unnecessary to plead other authority, e.g., jurisprudence or legislation, and such pleading is not of facts, the essence of pleading, but of law, which is not to be pleaded. Thus, I would direct that the sentences, phrases or references to particular conventions in paragraph 8 of the statement of claim and paragraphs 3(a), 3(b), 3(c) and 3(d) of the reply to demand for particulars be struck from the record.
 At paragraph 25 of his reasons, Justice MacKay decided this question as follows:
My opinion about the portions to be struck is based on my conclusion that those matters now to be deleted are immaterial and redundant to the plaintiffs’ claim. They do not state material facts, but rather they plead law, a matter not to be pleaded, for it is unnecessary to do so. Thus, I would strike them pursuant to paragraph 419(1)(b) of the Rules.
 Finally, I would like to refer to a Scottish High Court of Justiciary case, Lords Advocate’s Reference No. 1,  ScotHC 15,  S.L.T. 507. In that case, four individuals had been accused of crimes stemming from events that occurred aboard the Maytime while it was at anchor in the port of Loch Goil, Scotland. One of the questions that the Court had to answer was whether it was necessary to prove the content of customary international law. More specifically, as indicated in paragraph 21 of the Court’s reasons, the issue to be resolved was as follows: “In a trial under Scottish criminal procedure, is it competent to lead evidence as to the content of customary international law as it applies to the United Kingdom?” The following passages, found at paragraphs 23, 24 and 27, are relevant:
23. We are in no doubt that in relation to evidence in the trial itself this Question must be answered in the negative. A rule of customary international law is a rule of Scots law. As such, in solemn proceedings it is a matter for the judge and not for the jury. The jury must be directed by the judge upon such a matter, and must accept any such direction. There can thus be no question of the jury requiring to hear or consider the evidence of a witness, however expert, as to what the law is.
24. It was pointed out to us that evidence as to foreign law may competently be led in Scottish proceedings. This is because the law in question is foreign, and in Scottish proceedings is a question of fact and not of law. Any analogy between such foreign law and customary international law is false. . .
27. We can see some initial attraction in the suggestion that if a court is willing to read what a particular expert has written in a general context, it might on occasion be sensible to hear what he has to say, in the particular context of the case in hand. We do not feel it appropriate to rule out that possibility, as a matter of law. Such argument as was addressed to us in relation to Question 1 was of course directed primarily to the question of evidence in causa, before the jury; and while the possible usefulness of such material to a judge was touched upon, having regard to what the sheriff had said, the point was not fully argued. At that level, we are inclined to think that the matter would be one for the judge’s discretion, although we would wish to reserve our opinion on that point. We would, however, add that if in any particular situation it were thought necessary by those representing a party to have recourse to some specialist source of advice, the appropriate course would of course normally be to seek that advice, whether in writing or by consultation or both, so that the appropriate submissions could be made, by that party’s representative, at the appropriate time. In matters of customary international law, we can appreciate that the question of whether an opinio jurishas emerged, and won the general acceptance which is necessary to constitute a rule of customary international law, might well make recourse to expertise appropriate. But having regard to the different skills and expertise of an advocate on the one hand, and some other kind of specialist on the other hand, we find it very hard to imagine any situation in which the appropriate material should be presented to the court in the form of evidence with examination and cross-examination, and perhaps counter-evidence for the other party.
Of particular note here is Nadon JA’s emphasis upon the last-quoted passage from Lord Advocate’s Reference—a clear endorsement of the principle that international law is not a matter expert evidence. He concluded as follows (at ):
Consequently, I think that in a case like the one before us, the parties do not need to rely on expertise in international law. International law, being a question of law, is the prerogative of courts, which can take judicial notice of this law with the help of attorneys arguing the case.
While Nadon JA pointedly left open the possibility of reconsidering this matter in another case (having not heard submissions on the point), this discussion is bound to be significant. It must be regarded as something of a vindication of Prothonotary Morneau’s decision in Boily. More importantly, Nadon JA’s decision givesreason to hope that Canadian law will finally catch up with British and Australian authorities (notably Australian Competition and Consumer Commission v P. T. Garuda Indonesia (No 9) FCA 323) and treat opinion evidence on questions of international law as generally inadmissible. Some might insist that only a decision of the Supreme Court of Canada can settle the point, and certainly that would be a welcome development. But these three decisions, coming from the Canadian jurisdiction most experienced in international legal controversies, must be regarded as highly persuasive both within the federal court system and in the superior courts.