I don't think you can do this successfully. There is an unlock method in the Contact List Manager, but it is hard to understand the purpose of most methods (this also depends of your version of Sitecore).
Th best thing is to avoid the list to getting locked. This may be happening because of a bad handling of the contact. Whenever you unlock the list, anything could happen to both, the list and the contact (I even lost contacts by unlocking a list manually).
Let me know more about what you are trying to do.