Overriding and Blocking Group Policy
To enforce the Group Policy settings in a specific GPO, you can specify the No Override option. If you specify this option, policy settings in GPOs that are in lower-level Active Directory containers cannot override the policy. For example, if you define a GPO at the domain level, and you specify the No Override option, the policies that the GPO contains apply to all organizational units in that domain. Lower-level organizational units will not override the policy applied at the domain level.
To block inheritance of Group Policy from parent Active Directory containers, you can specify the Block inheritance option. For example, if you specify the Block inheritance option for an organizational unit, it prevents the application of policy at that level from higher-level Active Directory containers such as a higher-level organizational unit or domain.
Be aware that the No Override option always takes precedence over the Block inheritance option.
A local GPO cannot specify the No Override or Block inheritance option.
For more information, see Filtering the Scope of a GPO.