If the policy was specifically stated and the three in question signed it, I imagine they have no recourse.
That's why you have to be careful what things are thrust in front of you by your employer to sign. I know some folks who won't sign such policy things on principle. Typically, their refusal gets ignored.
I wonder why the employees were not given a warning first such as what one gets for too many tardies?
On a local note, we had an employee dismissed because she gave some medicine to a co-worker who then got sick from it.
A Free man or woman cannot sign away their Rights.