Interjurisdictional immunity

In Canadian Constitutional law, interjurisdictional immunity is the legal doctrine that determines which legislation arising from one level of jurisdiction may be applicable to matters covered at another level. Interjurisdictional immunity is an exception to the pith and substance doctrine, as it stipulates that there is a core to each federal subject matter that cannot be reached by provincial laws. While a provincial law that imposes a tax on banks may be ruled intra vires, as it is not within the protected core of banking, a provincial law that limits the rights of creditors to enforce their debts would strike at such a core and be ruled inapplicable.

The paramountcy doctrine proves that if a valid federal law and a valid provincial law conflict, the federal legislation is paramount, prevails and renders the provincial legislation inoperative to the extent of the conflict. The principal test for determining whether there is a conflict between the two laws is whether the provincial law "frustrates the purpose" of the federal law. In contrast, the interjurisdictional immunity doctrine is activated even if there is no meeting of legislation or contradiction between federal and provincial statutes. It requires only for the provincial legislation to impact federal things, persons or undertakings significantly. The doctrine renders inapplicable legislation of general application which affects the rights and obligations, impacts the status, or regulates the essential parts of:

• things,
• persons, or
• undertakings,

exclusively within the core of the jurisdiction of the other order of government.