Yes. If an employee leaves the company, it is possible to transfer their permissions for documents protected by SealPath to another user. This way, the employee who has left the company will no longer have access to these documents, regardless of where they are, whether on their home computer or mobile device, in a personal Dropbox account, etc.
You can see how to transfer document permissions here.
If you work in SealPath integrated with Active Directory or LDAP, if you change a user from one group to another, he/she will lose the access to the documents of the old group and will acquire the access to the documents of the new group.
You can see how to work with Active Directory/LDAP here.