East Midlands Trains is trying to use anti-union laws to stop industrial action by workers in the RMT union.
The High Court was set to decide whether to grant them an injunction on Tuesday of this week.
Staff have been on an overtime ban since last week over several issues.
The firm says this is an “invented dispute”.
It accuses the RMT of misleading workers.
If the court grants the injunction it could set a worrying precedent for letting bosses decide what constitutes a “real” dispute.
Many disputes start over a number of grievances, not just the one that is formally on the ballot paper.
This kind of ruling could be used against public sector workers who strike against privatisation.