Without non-solicitation agreement, you still *may* have recourse if the employee contacted clients whom he only knew of through his employment with you (basically using what would be called your "customer list" in a different business), because that is misappropriation of your business asset--an asset entrusted to the employee only to do his/her job, not for his/her own use--for his/her personal benefit. The employee can't contact clients he/she knows only from working for you and ask them to go with him/her, but he or she is not barred from taking them as clients (without a non-solication or non-competition agreement) if the client(s) contact him/her. The restriction is only on the employee using your information for his/her only benefit, not on working with your clients. However, this can be a difficult case to prove, and may not be worth taking action, especially for one or a small number of clients. For the future, making your employees sign a non-solicitation/non-competition agreement.