An administrator can add both computers and users to security groups. Then the administrator can specify which security groups are affected by the GPO by using the Access Control List (ACL) editor. To start the ACL editor, select the Security tab of the property page for the GPO. Then set access permissions using discretionary access control lists (DACLs) to allow or deny access to the GPO by specified groups. By changing the Access Control Entries (ACEs) within the DACL, the effect of any GPO can be modified to exclude or include the members of any security group. For more information about security groups, see How Security Groups are Used in Access Control.
To apply a GPO to a specific group, both the Read and Apply Group Policy ACEs are required. By default, all Authenticated Users have both these permissions set to Allow. Because everyone in an organizational unit is automatically an Authenticated User, the default behavior is for every GPO to apply to every Authenticated User. However, domain administrators, enterprise administrators, and the LocalSystem account already have full control permissions, by default, without the Apply Group Policy ACE. Therefore, because administrators are also …