Executive Summary: Key Legal and Evidentiary Issues

• The appeal turned on whether the Saskatchewan Labour Relations Board reasonably applied res judicata to bar the union's second certification application.
   
• Justice Kilback found that the Board conflated the doctrine of res judicata with the legal test for a nonsuit.
   
• A key evidentiary issue was whether res judicata operates as a rule of evidence that estops a party from contradicting a prior determination.
   
• Determining the correct nonsuit standard required assessing whether the union had adduced sufficient evidence on its certification claim, not on a change in circumstances.
   
• Whether res judicata applied was treated as a question of law requiring resolution before the nonsuit could properly be assessed.
   
• Ultimately, the reviewing judge's acceptance of a reasonableness standard did not shield the Board's decision from appellate intervention.
   

Facts of the case

KDM Constructors LP employs workers at the BHP Jansen Potash Project near Saskatoon. In the spring of 2020, Construction and General Workers Union Local 180 applied to the Saskatchewan Labour Relations Board to be certified as bargaining agent for a unit of labourers employed by KDM. On March 30, 2021, the Board dismissed that application, concluding the evidence did not establish that the proposed unit's work fell within the definition of "construction industry" under the governing legislation (the 2021 Decision). A subsequent reconsideration application was also dismissed. On January 17, 2022, the union filed a second certification application. KDM responded by seeking summary dismissal without an oral hearing, arguing the application was res judicata. The Board dismissed KDM's summary dismissal request, finding an oral hearing was needed to determine whether res judicata applied. The certification application was heard on October 13-14, 2022, and at the close of the union's case, KDM applied for a nonsuit on res judicata grounds. The Board granted the nonsuit and dismissed the union's application (the 2022 Decision). The union sought judicial review, but a Court of King's Bench judge found the 2022 Decision reasonable and dismissed the review application on July 30, 2025 (the Review Decision). The union then appealed to the Court of Appeal for Saskatchewan.

Policy and legislative provisions at issue

The certification application was brought under Part VI, Division 13 of The Saskatchewan Employment Act, which governs construction industry certification. Central to the dispute was section 6-65(a) of the Act, which defines "construction industry" — the Board's 2021 finding that the proposed unit's work did not meet this definition became the basis for KDM's later res judicata argument. KDM's application for summary dismissal invoked section 6-111(1)(o), which permits the Board to dismiss an application without a hearing. In response to the union's arguments on appeal, KDM also relied on section 6-111(1)(e), which allows the Board to receive evidence that might not be admissible in a court of law, and section 6-112(1), which provides that a technical irregularity does not invalidate a Board proceeding. On costs, the Court of Appeal applied Rule 54(1) of The Court of Appeal Rules in awarding costs of the appeal to the union.

Reasoning and analysis

Writing for the Court, Justice Kilback first addressed the standard of review. Although the parties had agreed reasonableness applied, the judgment noted that questions concerning when res judicata bars an administrative proceeding have sometimes been treated as attracting a correctness standard. The Court found it unnecessary to resolve this tension, since the 2022 Decision was unreasonable regardless of which standard applied. Turning to the merits, the Court identified two distinct legal concepts the Board had improperly merged. First, a nonsuit inquiry asks whether the party opposing the nonsuit has led sufficient evidence on all elements of its own claim — here, the union's case for certification — not whether there is sufficient evidence of some separate fact, such as a material change in circumstances. Second, res judicata is a rule of evidence that, once its preconditions are met, estops a party from adducing evidence to contradict a previously decided result; whether it applies is a question of law that must be resolved before assessing the sufficiency of evidence on a nonsuit. Instead, the Board asked whether there was sufficient evidence of a material change in circumstances since the 2021 Decision, effectively testing the res judicata question using the nonsuit standard, rather than first determining as a matter of law whether res judicata applied and then assessing the union's certification evidence. The Court rejected KDM's two defences of the Board's approach: the argument that the nonsuit test was indistinguishable from the Board's summary dismissal test was undermined by the Board's own express adoption of the common law nonsuit test from Ceapro Inc. v Saskatchewan; and the argument that the Board's flexible evidentiary powers excused the error was rejected because res judicata is a fundamental doctrine, not a mere technicality. The Board's failure to keep these two concepts separate meant its decision lacked the requisite justification, transparency, and intelligibility.

Ruling and overall outcome

The Court of Appeal allowed the appeal brought by Construction and General Workers Union Local 180, finding the reviewing judge erred in concluding the Board's 2022 Decision was reasonable. The Court set aside both the Review Decision and the 2022 Decision and remitted the union's application for construction industry certification to the Board for reconsideration. The union, as the successful party on appeal, was awarded costs of the appeal calculated in accordance with Rule 54(1) of The Court of Appeal Rules; the decision does not specify a dollar amount for these costs.