Para confirmar / negar os efeitos da política de grupo, execute rsop.msc
ou use GPResult
no cliente e veja o que eles mostram sobre as políticas de grupo aplicadas.
As possibilidades incluem "Grupos restritos" :
This feature enables you - as the administrator - to configure group memberships on the client computers or member servers. You can add user accounts to groups on client machines that are in the scope of the policy
Ou talvez, as Preferências da Política de Grupo "Grupo Local" :
The initial task of securing the local Administrators group is to ensure that the user no longer has membership in the group. This is easier said than done, since most companies have configured the user’s domain account to have membership in this group at installation of the user’s computer.
...As a perfect solution, you can use the Local Group – Group Policy Preference to accomplish the task within about 90 minutes of you implementing it.