No, constitutional conventions cannot stop free trade within Canada
I didn’t write about the “Free the Beer” decision, R. v. Comeau, 2016 NBPC 3, when it came out this spring. It took me a very long time to read, and others beat me to it ― notably Benjamin Oliphant, to whose excellent analysis over at Policy Options Perspectives there is not much to add. There is one specific point, however, which concerns a pet peeve of mine, and which I do not think others have addressed, which in my mind justifies my doing so here, however belatedly. The point in question is the government’s argument that a constitutional convention meant that section 121 of the Constitution Act, 1867 ought not to be invoked to strike down legislation erecting barriers to inter-provincial trade.
Justice LeBlanc rejected this argument, just as he rejected the rest of the Crown’s submissions on his way to concluding that New Brunswick’s rules prohibiting the importation of alcohol from other provinces are unconstitutional because contrary to section 121. But although there is much to like about his decision overall, I think there is a bit more to say about this particular point than he did.
The Crown claimed, on the basis of an expert report by a political scientist, that the ever-evolving Canadian federalism had developed in such a way that
governments, rather than the courts, have taken on the lion’s share of responsibility for the management of the federation. This is accomplished in part by the courts’ recognition of constitutional conventions and by a judicious deferral to governments to maintain the balance of powers. 
One of the conventions in question is, according to the Crown’s expert, the “disuse”  of section 121:
governments do not use section 121 to challenge the protectionist policies of other governments. As such perhaps a convention has formed whereby section 121 is effectively rendered inoperative. 
The expert, moreover, saw section 121 as a sort of spent transitional provision, arguing that it is rather a convention that prevents the imposition of customs duties at provincial borders.
Justice LeBlanc responded by pointing out, quite rightly, that
[o]nce the Supreme Court of Canada strictly interpreted section 121 [in Gold Seal Ltd. v. Alberta (Attorney-General), (1921), 62 S.C.R. 424, as applying only] to custom duties, there was in reality nowhere else for the section to go. It strictly prohibited custom duties and nothing else. Its disuse became merely a matter of practice or custom. It was not possible for the section to be interpreted in any way to come to the aid of any other governmental policy or strategy.
In other words, Supreme Court precedent limited the scope of section 121 ― though it certainly did not abolish it, so that it is fanciful to claim that a constitutional convention has been doing the work that this provision has always done ― and it is for that reason that it was no longer invoked. That is true, so far as it goes, and it is understandable that a judge would say no more in the course of an opinion that is already quite long enough. But, as I noted above, there is more to say here.
It is worth pointing out that the Crown’s reliance on constitutional conventions in the course of an argument is a pretty remarkable thing. On an orthodox view, constitutional conventions are not enforceable by courts. The Crown analogized section 121 to the provisions of the Constitution Act, 1867 that enable the Governor General (acting on the advice of the federal government, of course) to disallow provincial legislation, which are rendered inoperative by a constitutional convention. Yet the Supreme Court expressed the view, in Reference re The Power of the Governor General in Council to Disallow Provincial Legislation and the Power of Reservation of a Lieutenant-Governor of a Province,  S.C.R. 71, that these provisions were valid an in force as a matter of law. Similarly, in the Patriation Reference the Supreme Court said that conventions were not legal rules. So any attempt to invoke conventions as a sword rather than a shield (arguing that a claim should not be entertained because it asks the court to enforce conventions) faces an uphill battle, and indeed seems pretty desperate. It is telling, I think, that the Crown chose to make such an argument in Comeau.
Now, my own opinion is that the orthodox view that there is a sharp distinction between conventions and law is unfounded. Fabien Gélinas and I have suggested that, at least, conventions should inform the interpretation of the provisions of the written constitution. In a paper called “Towards a Jurisprudence of Constitutional Conventions”, (2011) 11:1 OUCLJ 29, I went further and argued that courts could actually treat conventions the way they treat common law constitutional rules, subject to justiciability concerns. While it is far from obvious that courts would endorse either of these approaches, and not very clear that the Crown in Comeau made much of an argument to show that they ought to, let’s assume that the court would have been bound to take a relevant convention into account in one way or another. Of course the question is whether there is such a convention here. Justice LeBlanc’s reasons suggest that the answer is “no.” But they ― understandably ― do not go into any detail on this point. A closer look shows that the Crown’s argument is completely off-base.
All constitutional conventions limit or eliminate he discretion that political actors seem to enjoy pursuant to other constitutional rules. For example, the law of the constitution leaves the sovereign with the choice to assent or not to bills that have passed the House of Commons and the Senate, but convention eliminates this discretion. The sovereign must assent. Geography does not figure among the criteria which the Supreme Court Act provides for the appointment of Supreme Court judges, other than those from Québec, but convention reduces the government’s discretion as to the advice it gives the Governor General by supplying additional geographic requirements.
What about the alleged convention here? The Crown’s expert points out that governments have refrained from suing each other on the basis of section 121. But even if that forbearance could be said to have acquired the status of a conventional rule, this convention could apply to governments ― the political actors whose behaviour contributed to the alleged rule’s emergence ― and only to governments. Not to citizens. To repeat, conventions stipulate how political actors exercise discretion. They do not dictate the behaviour of citizens. So while a convention may in effect nullify constitutional provisions that only empowers a political actor, such as those dealing with the disallowance power, they cannot “render inoperative” provisions that confer rights on citizens.
The Crown’s argument assumes, without even attempting to demonstrate, that section 121 is a provision that only concerns governments. But the assumption is unwarranted, and indeed galling. Constitutional provisions limiting the power of governments, such as section 121, exist in order to preserve the liberty of the citizens. In Attorney General of Nova Scotia v. Attorney General of Canada,  S.C.R. 31, Chief Justice Rinfret wrote that even if Parliament and the legislatures agree to modify the constitutional division of powers by resorting to delegation, they cannot do so, because
[t]he constitution of Canada does not belong either to Parliament, or to the Legislatures; it belongs to the country and it is there that the citizens of the country will find the protection of the rights to which they are entitled. (34)
As the Chief Justice pointed out,
[i]t is part of that protection that Parliament can legislate only on the subject matters referred to it by section 91 and that each Province can legislate exclusively on the subject matters referred to it by section 92. (34)
But another part of that protection, of course, is that when the constitution removes a legislative power from both Parliament and the provinces, neither can arrogate such a power to itself, even with the connivance of the other. This is true of the power of constitutional amendment, for instance, and of the violation of Charter rights. And it is equally true of section 121. Were a court to accept to Crown’s (un)conventional argument to the contrary, it would transform the Canadian constitution from protection of the citizens’ freedom into a plaything for governments intent on limiting that freedom.