Joseph Ryan and his brother David died when their fishing boat capsized off the coast of Newfoundland. Their widows and dependents received compensation under the provincial Workplace Health, Safety and Compensation Act(WHSCA). Section 44 of the WHSCA bars other claims by a worker (or a worker's estate or dependents) where compensation has been paid under the statute. The estates of the brothers did want to sue other parties in proceedings under the federal Marine Liability Act (MLA): the builder of the vessel for negligence in design and construction, and the federal government for negligence in inspection of it. Were these claims barred by section 44?

The provincial workers' compensation commission upheld the s 44 bar. Judicial review of that decision resulted in its being overturned: liability in the marine context is within exclusive federal jurisdiction and the right to make a claim under the MLA a core feature of that power, which was impaired by the s 44 bar. The doctrine of interjurisdictional immunity required s 44 to be read down so as not to impair the MLA rights of the brothers' estates; and the doctrine of paramountcy also applied because it was impossible to comply with both the federal and provincial statutes. This was upheld by the majority of the Newfoundland and Labrador Court of Appeal, with Welsh JA dissenting.
Justice Welsh reckoned that there was no operational conflict between the MLA and WHSCA: the WHSCA removes the right of a deceased person to recover damages, while the MLA simply says that dependents 'may' start an action 'under circumstances' where the deceased would have been entitled to do so. In other words, a MLA claim may be advanced unless there is a statutory reason why they may not -- a statutory reason like s 44 of the WHSCA. Interjurisdictional immunity did not apply because the WHSCA (a workers' compensation scheme) does not trench on the core of federal power over shipping and navigation, and does not deal with negligence.
Turns out Justice Welsh was right, according to a unanimous Supreme Court of Canada: Marine Services International Ltd v Ryan Estate, 2013 SCC 44. Interjurisdictional immunity is limited to situations where a provincial law not only trenches on federal jurisdiction but does so in a 'sufficiently serious' way that not only affects but also impairs federal power. Not the case here. Nor did paramountcy come into play, because the WSHCA was not inconsistent with the MLA and did not frustrate its purpose. The two have different purposes: one provides no-fault insurance benefits for workplace injuries, while the other establishes a statutory tort regime and expands the range of claimants who could bring an action in maritime negligence law. Allowing the two statutes to work together also ensured consistency between the WHSCA and federal workers' compensation schemes.