Yeah, I've been learning that the hard way, and after reading thru dozens of posts on this forum I'm getting a feel for how much worse it could get, like in those "at will" states.
Here's the latest, and I know it's not going to be something that the company could be sued over. It's an example of how our union leadership is sitting on their hands.
Our contract clearly states (big bold letters) that 25% of any "work group" can be off on vacation at any time. The wording was put in place long ago. 25 years or more. Employer doesn't like it because they have to pay overtime every once in a while to cover the work. We're an operations crew; the demand is 24/7.
So they've reinterpreted "work group" to say that it's not the entire group or classification of workers across all four shifts (roughly 40 employees), it's just one crew. They're saying that computes to one person at a time off on vacation. If you add up all of our accrued vacation, there aren't enough days in the year even if the company forced people to use theirs during the least desirable times. Their response to that - "we'll let you carry it over". So the next year the overflow will be worse, and the next year - well, you get the idea.
The hall is going thru the grievance process. The grievance process costs money at the third step and the company knows that's where the union drops it. If the union rolls over on this, the co. will know they can do anything.
Here are some quick examples with less detail.
A supervisor turned down an employee's vacation request, and just penciled him in on a Monday, telling the employee that worked out better for the company. Did it twice to the same employee.
Our product is being received by train now. Couple of years ago the company came out and said we have to stay at our posts til relieved when a train's unloading. We have an overtime policy. It's been written in stone for years. It determines who's asked for overtime (not forced) using a "redtime" list that tracks overtime either worked and/or turned down. Now you get the overtime, it's mandatory, makes no difference if you're high on redtime or low, junior or senior. The only factor is whether your position during that shift is tied to the train or not. Union has done nothing even though this clearly undermines the entire overtime policy and sets some scary precedents.
Company has started "mandatory" meetings on our off-hours. We work 12 hour shifts. The job isn't fun. I value my time off. Latest example - they're having some sort of "Safety Awareness" meeting in a town that's 20 miles away from the work site. It's "mandatory".
I got a letter a few months back when the supervisor got on the radio at the end of a long nightshift and said we all had to hold over to cover the next crew, who was going to a "meeting". We've never been forced to hold over unless it was some sort of operational emergency. I said I didn't think they could hold me over, I felt sick, and wanted to go home. The supervisor said it was awful suspicious that I suddenly got sick, and said I should leave right now or cover the overtime. I stayed, scared of what might happen if I didn't. As I was rounding up my lunchpail, the supervisor "thanked" me. I told him there was no thanks involved, I did it because I was scared not to. I got a letter for "unprofessional" and "disrespectful" behavior and 2 days suspension.
Another operator volunteered to play Santa at the annual Kid's Christmas Party, held early in the evening. He shows up with his Santa suit. A secretary, not a supervisor, tells him that someone called in sick and he "has" to report to work. Although unhappy about it, he went. I have no idea who filled in as Santa for the kids

He e-mailed to the guy up the food chain above his boss, complaining about being forced to work, and being forced by a secretary at that. He got a letter for "unprofessional" and "disrespectful" behavior and time off without pay.
Another operator was spotted without his seatbelt buckled in a forklift. Co. tried to fire him on the spot, saying he had a history of unsafe actions. The week before a supervisor caught him coming out of a dusty area, and taking off his hardhat to bang the dust off. Taking the hardhat off for a few seconds apparently counted as a violation.
I realize that none of the above is enough to go to court and sue the company or union for millions of dollars. Us laypeople get funny ideas about how the legal system works from TV. But there's a frightening pattern evolving and I want to know if there's any way to get ahead of it. I'm one "unprofessional" comment away from being fired (28 year employee) and several others are on thin ice too. The union has always been unreliable and a little squirrely, but lately they're just out to lunch.