Yup, it's often a "Work To Rule" action [1], where everyone works exactly by the book. All shortcuts are eliminated, every break is taken to the exact second (instead of working through the breaks to get stuff done), etc. Everything slows down, and that is that.
And the point is that it is strictly legal - everything is being done exactly by the book. Even so, employers sometimes sue unions over "malicious compliance".
Another way that works in many fields is just everyone refusing any and all overtime. If everyone does that most companies (and police, fire departments, public hospitals, etc) can't cope.
The company can't really force anyone to take extra overtime. The only thing they can do is fire you (well not in the Nordics but in the US I think yes?) but that will only make their problem of not having enough workers around worse.
And the point is that it is strictly legal - everything is being done exactly by the book. Even so, employers sometimes sue unions over "malicious compliance".
[1] https://en.wikipedia.org/wiki/Work-to-rule