Well of course it depends on the employment law used in your particular jurisdiction, and on whether or not you have a collective agreement in place which governs cause for dismissal. But what one can say is that (generally) in common law jurisdictions like England (but not Scotland), most Commonwealth nations and the United States (less Louisiana)) employers are free to fire employees at will, with or without cause. The question becomes one of how much compensation the employee is entitled to, which (again) will be dependent upon local employment law, length of service, any applicable collective agreement, and the cause (if any) for the dismissal.

You would have brilliant grounds to sue them if you did, unless you had a contractual agreement in position not to do it first...if such an agreement is legal.