Define/control which users/role(s) can change change to a specific state of work items?
One answer
You can define which Role can trigger which workflow action here:
Project Area - Process Configuration tab - Team Configuration - Permissions (click 'Show all actions and roles') - Work Items - Save Work Item (server) - Trigger a workflow action ... click only those Roles which you want able to e.g. Close a Defect.
(not sure you can further define this at specific user level)
Comments
You can't have different permissions based on whether or not a user created the work item. There is no way to say the equivalent of "allow this for a certain role plus the creator of the work item." The permissions for "Everyone" truly means everyone. If you want to restrict a certain state transition to a certain role, then you have turn off the permission for the "Everyone" role.