All we can do is wait for the contract to finish and then not renew it. Its perfectly legal, a lawyer told me.
Believe me, they know how to cover their backs.
What they really don't want to do is to lose the billable position. In practice, a lot of people will just suck it up to the end of the contract and then leave, especially if the contract is less than a year.
In practice, they will probably not do that as the HR team is busy with other things and the lawsuit might be bad PR, although a hiring manager that wants to get back to you for doing that might have the HR department sue you, legally they could do that.
Sometimes I think an international one-week walk-off by IT staff would do wonders for the worker-employer relationship.