 Interjurisdictional immunity should in general be reserved for situations already covered by precedent.In practice, it is largely reserved for heads of power that deal with federal things, persons, or undertakings, or if, in the past, its application has been considered absolutely indispensable or necessary to achieve the purpose for which exclusive legislative jurisdiction was conferred, as discerned from the constitutional division of powers as a whole, or what is absolutely indispensable or necessary to enable an undertaking to carry out its mandate in what makes it specifically of one jurisdiction or the other.While in theory, a consideration of interjurisdictional immunity is apt for consideration after the pith and substance analysis, in practice, the absence of prior case law favouring its application to the subject matter at hand will generally justify a court proceeding directly to the consideration of federal paramountcy.