An Ontario labour arbitrator has refused to summarily dismiss a United Steelworkers grievance against Magellan Aerospace but narrowed it to a single ground, ruling the union can pursue its complaint only if it relies on a promise the company allegedly made at the bargaining table.
The grievance, filed by Local 2021 on Feb. 20, 2026, challenged an operational change the company introduced on Feb. 7. The union said the company broke a longstanding practice of shutting down all machines at the end of the last shift. On that Saturday, a robot cell operator was directed to leave the machines running unattended until the part was finished.
The union sought an immediate stop to the change and asked that all seven robot cell operators be paid at time and a half “for the length of time the cell ran unattended.”
The employer raised a preliminary objection, arguing the grievance disclosed no prima facie case of any breach of the collective agreement and should be summarily dismissed. It pointed to a broad management rights clause reserving to the company the exclusive function to maintain efficiency and to determine the kinds, locations and control of equipment, work schedules and production standards.
The estoppel dispute
The company argued the union was attempting to ground an estoppel in the exercise of a management right, which it said the authorities do not permit. It relied on a line of arbitral decisions holding that the mere existence of a past practice, however long, cannot freeze that practice or convert it into a collective agreement right where the practice relates only to the exercise of management rights and is not tied to any negotiated language.
The union framed its case as one of estoppel. It noted the collective agreement provides that “CNC and CMM machines will normally run unattended through breaks,” language it said the company proposed in 2001 bargaining and that the union’s predecessor accepted only in exchange for a longer break period. The union said the parties had since operated on the understanding that the machines would run unattended during breaks but would not continue running without an operator after the final shift.
To establish estoppel, the union pointed to two things. It said the company made a representation during the most recent round of bargaining, in December 2025, that it would continue limiting unattended operation to breaks. It also said it had relied on the company’s silence in bargaining as assurance the practice would continue, and that it would have negotiated a change had it thought otherwise. The union added that running the machines after employees left denied operators overtime and raised safety concerns.
In reply, the company identified a conflict in the union’s position, noting that the union asserted both that a representation had been made and that it had relied on the company’s silence.
The arbitrator’s findings
The arbitrator found the union had not answered the central point: that the mere subsistence of a practice, without more, is not enough to ground an estoppel. The practice the union relied on was not contrary to any express provision of the collective agreement, while the management rights clause amply provided for the company’s decision to require operators to leave machines running to complete cycles after their shifts.
The arbitrator determined the final sentence of the break provision speaks only to the running of machines during breaks and says nothing about other times. Nothing in the language suggested the company’s right to allow machines to run unattended at or after the end of a shift was limited by the agreement.
He treated the circumstances of the 2001 bargaining and the alleged consequences for overtime and safety as having no bearing on whether the union had presented a prima facie estoppel case. The arbitrator found the only material factual content was the allegation that the company made a representation in December 2025 on which the union relied in declining to seek a language change. The competing assertion that the union relied on the company’s silence was immaterial and could not, on its own, disturb the exercise of management rights.
The arbitrator concluded the grievance could survive the motion only if the union proceeded on the alleged December 2025 representation. Although the company denies making it, he was required to assess the grievance without reference to facts alleged by the employer, and found that such a representation, if made, could support a finding that the company was estopped from changing the practice on Feb. 7.
The union was allowed to proceed on that single ground, provided it delivers full particulars and all arguably relevant documents to the company by June 16, 2026. To the extent the union relies on the company’s alleged silence, the grievance will be dismissed. The arbitrator also ruled that the union will be taken to have withdrawn the representation allegation if it fails to deliver its particulars and productions as directed.
Counsel for Plaintiff
Mary Lou Scott and Nadia Crystal, United Steelworkers, with local executive members Isaiah Argunen, Mark Crawford, Bryan Wright, Jim Crawford and Martin Sookhoo.
Counsel for Defendant
Kenji Nuhn, Hicks Morley Hamilton Stewart Storie LLP.
Decision Maker
Derek L. Rogers, Arbitrator.
For more information, see Magellan Aerospace, Kitchener, a division of Magellan Aerospace Limited v. United Steelworkers, on behalf of Local 2021, 2026 CanLII 51870 (ON LA).
