Joined: 06 April 2009
I'm not a lawyer, but I'm willing to give a personal opinion if it will help.
If you mean with out the employees knowledge then I would think that this may be amoral if not illegal. If the locker belongs to the company, there should be no problem in asking the employee to remove his or her stuff from the locker by a deadline and inform them that the locker will be emptied if they do not comply.
If you suspect the employee of a crime, then you can treat it a disciplinary offence and confront the employee and ask them to empty their locker, or a crime and call the police. Some employment contracts have a clause to allow an employee to be searched. It may be worth considering this in future employment contracts. Your company should also have an employees handbook which defines the rights of the employees on site.
Hope this helps