Extremely sorry for the delay. I was out on sick.
Once the license key is activated on a domain it will be registered with it. It will not be deregistered automatically unless manually requested with a valid reason.
The reason we do not allow user control on deregistration is that, it allows unlimited activation of the key.
I can sure help you deregister the domains the with license key.
Please let me know the list of domains, I will make the changes on the license server and update you.