Here is a stray thought inspired by the discussion of interjurisdictional immunities in the Supreme Court’s decision in Rogers Communications Inc. v. Châteauguay (City), 2016 SCC 23, about which I wrote yesterday. One way in which the Supreme Court has, or so it is often claimed, dismissed originalist constitutional interpretation is by comparing it to a theory of “frozen concepts” which cannot evolve as the times require. In Reference re Same-Sex Marriage, 2004 SCC 79,  3 S.C.R. 698, the Court proclaimed that
[t]he “frozen concepts” reasoning runs contrary to one of the most fundamental principles of Canadian constitutional interpretation: that our Constitution is a living tree which, by way of progressive interpretation, accommodates and addresses the realities of modern life. 
Speaking extra-judicially, then-Justice Binnie went one step further and referred to “a theory of frozen rights with no realistic prospect of a thaw.”
However, as Benjamin Oliphant and I explain in a recent paper, equating originalism with a simple belief that the concepts used in a constitutional text are “frozen” reflects a misunderstanding if not a misrepresentation of contemporary originalism, at least, or especially, of contemporary originalism which accepts a distinction between constitutional interpretation and construction. Indeed, as we further argue, the Court itself occasionally resorts to originalist reasoning, some of which could arguably be described as reflecting a “frozen concepts” view of constitutional law.
Be that as it may, the doctrine of interjurisdictional immunities is probably the single best example of a “frozen concept” in Canadian constitutional law. In Canadian Western Bank v. Alberta, 2007 SCC 22,  2 S.C.R. 3, the majority opinion stated that
interjurisdictional immunity is of limited application and should in general be reserved for situations already covered by precedent. This means, in practice, that it will be largely reserved for those heads of power that deal with federal things, persons or undertakings, or where in the past its application has been considered absolutely indispensable. 
The majority in Rogers Communications quoted this passage with approval, and approach the issue of interjurisdictional immunity accordingly, asking whether there was precedent for treating the location of radiocommunications equipment as belonging to the “core” of the federal power over radiocommunications.
This is not, strictly speaking, originalism. Along with the whole machinery of “pith and substance,” “double aspect,” and “paramountcy,” it is a creature of constitutional construction ― the judicial development of doctrines necessary to give effect to a constitutional text, which is often insufficient to resolve a dispute on its own. (Canadian Western Bank sets out this development in great detail.) Constitutional construction, as Randy Barnett for example has argued, is not itself originalist ― only interpretation can be.
Yet the idea that interjurisdictional immunity is alive and well ― but only in those areas where there is precedent for its application is nothing if not the “freezing” of a constitutional concept ― albeit one developed by judges rather than provided by the constitutional text. For close to a century, the doctrine developed in fits and starts ― and then, in 2007, Justice Lebel and, of all people, Justice Binnie concluded that that was it, and that the time had come to freeze it in its then-current state. This decision is rather puzzling. For one thing, it seems to sit uneasily with the Supreme Court’s oft-repeated commitment to “living-treeism” ― reiterated in Canadian Western Bank, where the majority opinion insists that “the interpretation of [legislative] powers and of how they interrelate must evolve and must be tailored to the changing political and cultural realities of Canadian society.”  And for another, it is not clear that the normative arguments for treating a statutory or constitutional text as “frozen” until amended by the body that enacted it apply to a judicially-developed doctrine ― or at least that they can support a “freezing” of such a doctrine deeper than that effect by the usual principles of stare decisis.
Whether or not treating it in this way makes sense, the doctrine of interjurisdictional immunity is a “frozen concept” in Canadian constitutional law. It is one more reason to treat judicial protestations to the effect that such things are unknown this side of the border as too much. Slogans do not help us understand constitutional law, or anything else.