Hey there, thanks for writing in! 

There isn't a direct way to restrict user access for Team Spaces or specific reports at the moment. Admins and Managers have the ability to control who is able to invite and add content to a specific space, but this doesn't prevent users from just joining a team space.
 

The only other thing that I've seen customers do is if they are setting specific project permissions (Enterprise offering) and limiting the access that way.

Our project-level permissions and permission groups are available for Enterprise customers who need the ability to better target levels of security. Please feel free to reach out to the Sales team if you would like to know more about it and the pricing! 

Best,

Zhenia