Can I force someone to release ownership of a web domain name?

Perhaps. Find several TN licensed attorneys with domain name dispute experience and request some consultations. You can use to locate such attorneys and some may respond to your posted question as well that you can then contact. Be prepared to provide much more in the way of facts, such as written contracts, email correspondence, did you initially register the domain in your name, is the domain name the same as your trademark, whether the contractor is a contractor or an employee, etc.

It really depends on the specifics of the situation. You may be able to sue the contractor for something akin to conversion if the domain was clearly yours. If the domain name is your trademark, there could be other more difficult was of regaining control, i.e. suing under the cyber squatter act.

You could benefit from meeting with an attorney to discuss further. Even if you decide not to hire the attorney the consultation with him or her could help you to understand the issues and your options. Many attorneys offer a free consultation. I wish you the best and Merry Christmas.