At this time the group administrator could enable and allow certain users to enter free form tags, but no to block the use of tags.


> ###Tags
> 
> Tags are special words used to associate topics with subject areas.
> Tags are created by administrators (or members with the "enter free
> form tags" permission) for the group and then applied by members to
> individual topics. For example, an administrator of a group called
> "Smart Phones" might create a tag called "android." Group members can
> assign this tag to topics in the group to identify the subject as
> relating to "android." Other group members can search on topics with
> the tag "android" to find related topics.

**References**  
[Enable and create tags for a group - Groups Help](https://support.google.com/groups/answer/1311298?hl=en)  
[Permissions - Groups Help](https://support.google.com/groups/answer/2465496?hl=en)