What can I legally do to an employee who is working on the side creating a conflict of interest?

If I own a company (that tutors many subjects) and one of my tutors is working for me as well as tutoring on the side, what course of action do I have besides the threat of litigation because upon employment that employee signed a contract stating that he could not be employed by any other company or self that was a "conflict of interest"? If the company is accredited through the state of Texas is there anyway I could go the route of something like academic dishonesty? ... especially if I hired him/her through the local university and they are currently grad students?