An arbitrator ruling says Nemak violated its collective agreement with Unifor Local 200 when it closed the Windsor Aluminum Plant and moved production to Mexico.
The ruling was released Thursday, but Unifor announced the decision on Friday.
"Yesterday's ruling delivers an important victory for our members and our union," said Unifor National President Jerry Dias. "This decision brings us one step closer to a just outcome for our members who have displayed incredible determination despite enormous hardship and loss."
Nemak announced it would close its operation in Windsor almost two years ago.
Unifor argued the decision went against a collective bargaining agreement it reached with the company in 2015. Nemak had contractually promised it would build two General Motors engine blocks in Windsor if the workers agreed to a pay freeze until 2022.
The dispute reached a new level when members of the union launched a blockade at the plant on Labour Day 2019. During the two-week protest, both the Ontario Labour Relations Board and a Windsor judge ordered Unifor to remove the blockade. They ignored both orders until the company agreed to sit down with union officials and discuss the closure.
The dispute went to arbitration, and Arbitrator Norm Jesin ruled at first the plant could close. However, an Ontario court disagreed and sent the issue back to Jesin.
Now, it goes back to Nemak and Unifor Local 200.
"This is the decision we were hoping for," said Unifor Local 200 President John D'Agnolo. "It proves what we've been saying all along; that the company violated the work commitment provisions of our collective agreement. Now, we can roll up our sleeves and get appropriate remedies for our members."
The plant employed 270 people.