The issue for the Court was whether the statutory bar created by a provincial workers' comp scheme was inapplicable or invalid on the basis that it prevented the claimants from bringing an action in negligence under federal legislation on maritime law. Laws relating to the high seas fall clearly within federal jurisdiction and the claimants (the dependents of two brothers who died at sea) alleged that it was constitutionally inappropriate for provincial law to interfere with federal law claims.
In resolving the issue of paramountcy (i.e. whether there was a conflict between the provincial and federal statutes at issue), the Court had to consider the nature of workers' compensation. In the following passage, the WHSCA is the provincial law, the MLA the federal:
Workers' compensation tribunals find themselves in a tricky position. On the one hand, to slavishly follow the letter of tort law developed by courts would defeat the purpose of taking workers' compensation out of the courts in the first place. On the other hand, their constitutive statutes will often contain provisions or principles that are drawn from or heavily influenced by the common law of tort. (See my previous post on causation here). Second, the WHSCA and the MLA are distinct in purpose and nature: the first provides no-fault insurance benefits for workplace-related injury and the second is a statutory tort regime. In Workers’ Compensation Appeal Board v. Penney (1980), 38 N.S.R. (2d) 623 (C.A.), Jones J.A. stated that “the principles of tort law have no application to workmen’s compensation legislation” (para. 13). In Ferneyhough v. Workers’ Compensation Appeals Tribunal, 2000 NSCA 121 (CanLII), 2000 NSCA 121, 189 N.S.R. (2d) 76, Cromwell J.A. (as he then was) considered that statement:Of course, one of the purposes of a workers’ compensation scheme is to take compensation for work injury and occupational disease out of the fault based tort system. Concepts such as “fault” and “damages”, so central to tort law, are not consistent with the purposes of the workers’ compensation scheme. It was in this general sense that Jones, J.A., stated that tort law principles do not apply to the workers’ compensation system. [para. 15]More recently, Cromwell J.A. stated that “[t]he overall purpose of workers’ compensation legislation is to take decisions about compensation for workplace injuries out of the tort system and out of the courts”: Nova Scotia (Minister of Transportation and Public Works) v. Workers’ Compensation Appeals Tribunal, 2005 NSCA 62 (CanLII), 2005 NSCA 62, 231 N.S.R. (2d) 390, at para. 20.
The approval of Cromwell J.A.'s comments will presumably give (further) licence to workers' compensation tribunals to focus more on the principles and policies of their constitutive statutes than on the intricacies of tort law doctrine.
One other interesting aspect of today's decision is the confirmation that the doctrine of federal paramountcy applies only as between provincial and federal statutes. Common law doctrines are untouched:
So (if I understand correctly), even though federal common law regulates maritime negligence actions, these can be barred by provincial workers' compensation legislation without constitutional difficulty (though see also para. 64 for the Court's summary of why interjurisdictional immunity does not apply). Had the Ryan brothers survived, neither interjurisdictional immunity nor federal paramountcy would apply so as to render the statutory bar in s. 44 of the WHSCA constitutionally inapplicable or inoperative. Interjurisdictional immunity would not apply for the same reasons that it does not apply to the circumstances of this appeal. As discussed earlier, federal paramountcy only applies where there is an inconsistency between two valid legislative enactments — one federal and one provincial. It does not apply to an inconsistency between the common law and a valid provincial legislative enactment. Accordingly, if the Ryan brothers had survived and sought damages in tort, federal paramountcy would not have applied to render the statutory bar in s. 44 inoperative.
For an interesting article on the history of workers' compensation schemes, see here.
Readers may also be interested in Walsh v Mobil Oil Canada, 2013 ABCA 238, a case on the appropriate level of damages for a breach of provincial human rights legislation. The complainant had a variety of ailments, some of which seemed to have arisen as a result of her mistreatment by her employer but -- as is common in tort cases -- figuring out who or what caused what was difficult. The Court of Appeal made some interesting observations on causation:
 A causation analysis of some form is therefore required. The causation analysis that springs to mind is that utilized in tort law, the “but for” test. The plaintiff must show that “but for” the defendant’s negligent acts (here read discriminatory for negligent) the injury would not have occurred. The “but for” test is challenging to apply in circumstances where there may be multiple independent causes that are alleged to have brought about a single harm, such as we have here. This difficulty may justify relaxing the requirement of “but for” causation and finding liability on a material contribution to risk approach. However, the jurisprudence to date has not required such a precise analysis in human rights cases. The most that can be said is that tribunals have drawn from contract and tort law, particularly by importing the need for a causal link and the duty to mitigate, to ascertain the amount and extent of wage loss damages sustained as a result of discriminatory conduct. (my emphasis)
 Having regard to the standard of review, we cannot say Ms. Bryant’s decision is unreasonable. We are not certain that the tort analogy withstands scrutiny. We note, however, that this is an egregious case both in terms of the wilfulness of Mobil’s conduct, the duration of that conduct, the damaging impact on the appellant, and the untenable position that Mobil maintained throughout the litigation that the appellant was terminated for cause. The record is replete with evidence of the negative impact Mobil’s conduct had on the appellant’s self respect and confidence. Both awards are on the low end of what we would consider appropriate in the circumstances, but the standard of review does not permit our interference.