The restricted groups option allows you to modify the current group configuration and membership on your client computers. When this policy is applied to workstations and servers, their individual group configurations are modified to match that configured inside the policy. The policy contains members and members of lists that overwrite any configuration on the target computers. For example, if you were to add the Administrator group to the policy but not add any users to the members of this group list, and then you applied the policy, Windows would remove any users currently in those groups on the client computers. However, the other facet of the policy, groups of which the added group is currently a member, is only additive: if the list is empty, no modifications are made to the client computers. Only additions are processed and changed.
Only the groups listed inside the Details window of the Restricted Groups policy branch can be modified using the policy, but it's a great way to keep individual users from modifying powerful groups on their own systems.
To modify the restricted groups policy, do the following:
Launch the GPMC, and then right-click on your target GPO in the left pane and select Edit.
Inside the Group Policy Object Editor, navigate through Computer Configuration, Policies, Windows Settings, and Security Settings.
Right-click the Restricted Group branch and select Add Group from the context menu.
Click the Browse button, and select any group currently inside your directory. Click OK.
Now, right-click the newly added group, and select Properties from the context menu.
Add the users that belong to this group to the "Members of this group" list, and add the groups within which this group is nested to the "This group is a member of" list. Use the Add button in both cases.
When you're finished, click OK to close out the boxes.