Constitution - Provincial and Inter-provincial. Alberta (Attorney General) v. British Columbia (Attorney General)
In Alberta (Attorney General) v. British Columbia (Attorney General) (Fed CA, 2021) the Federal Court of Appeal considered a rare intergovernmental (province-to-province) dispute, where BC sued Alberta and there were suggestions of raw politics afoot (quoting from the minority ruling):
 In the legislative debates leading to the passage of the Act, members of the Alberta legislature made statements suggesting that the Act’s true purpose was political retaliation. That is, the Act would allow Alberta to restrict the flow of natural resources to British Columbia as a response to the latter’s opposition to the Trans Mountain pipeline expansion. ...The case focussed on this provision of the Federal Court Rules:
 On May 1, 2019, the Attorney General of British Columbia (BC) commenced an action before the Alberta Court of Queen’s Bench (the Alberta Court) seeking a declaration of invalidity in respect of the Act. Alberta responded to BC’s action by filing a motion to dismiss it on the grounds that the Alberta Court had no jurisdiction to entertain the proceedings and that BC lacked standing to bring its action.
 Pending the resolution of the above issue, BC commenced an action, pursuant to section 19 of the Federal Courts Act, R.S.C. 1985, c. F-7 (the FCA) in the Federal Court on June 14, 2019, in which it sought a declaration that the Act was unconstitutional. ....
Intergovernmental disputesQuoting from the majority ruling, the case sets out the range of cases that FCA s.19 is meant to address (more than solely Crown rights disputes) - and the fact that Alberta did not dispute that the Federal Court had such jurisdiction per se (the ITO test). The majority reached this first conclusion by reviewing the provision in light of principles of statutory interpretation [paras 115-168].
19 If the legislature of a province has passed an Act agreeing that the Federal Court, the Federal Court of Canada or the Exchequer Court of Canada has jurisdiction in cases of controversies between Canada and that province, or between that province and any other province or provinces that have passed a like Act, the Federal Court has jurisdiction to determine the controversies.
. R. v. Comeau
In R. v. Comeau (SCC, 2018) the Supreme Court of Canada considered the constitutional provision that holds that "All Articles of the Growth, Produce, or Manufacture of any one of the Provinces shall, from and after the Union, be admitted free into each of the other Provinces." [s.121, Constitution Act, 1867] at paras 44-116.
. Club Resorts Ltd. v. Van Breda
In Club Resorts Ltd. v. Van Breda (SCC, 2012) the Supreme Court of Canada commented on little-discussed constitutional law between provinces:
(3) Constitutional Underpinnings of Private International Law
 Conflicts rules must fit within Canada’s constitutional structure. Given the nature of private international law, its application inevitably raises constitutional issues. This branch of the law is concerned with the jurisdiction of courts of the Canadian provinces, with whether that jurisdiction should be exercised, with what law should apply to a dispute, and with whether a court should recognize and enforce a judgment rendered by a court of another province or country. The rules of private international law can be found, in the common law provinces, in the common law and in statute law and, in Quebec, in the Civil Code of Québec, S.Q. 1991, c. 64, which contains a well-developed set of rules and principles in this area (see Civil Code of Québec, Book Ten, arts. 3076 to 3168). The interplay between provincial jurisdiction and external legal situations takes place within a constitutional framework which limits the external reach of provincial laws and of a province’s courts. The Constitution assigns powers to the provinces. But these powers are subject to the restriction that they be exercised within the province in question (see P. W. Hogg, Constitutional Law of Canada (5th ed. 2007), vol. 1, at pp. 364-65 and 376-77; H. Brun, G. Tremblay and E. Brouillet, Droit constitutionnel (5th ed. 2008), at p. 569; British Columbia v. Imperial Tobacco Canada Ltd., 2005 SCC 49,  2 S.C.R. 473, at paras. 26-28, per Major J.), and they must be exercised in a manner consistent with the territorial restrictions created by the Constitution (see Castillo v. Castillo, 2005 SCC 83,  3 S.C.R. 870, at para. 5, per Major J.; Unifund Assurance Co. v. Insurance Corp. of British Columbia, 2003 SCC 40,  2 S.C.R. 63, at para. 51, per Binnie J.).