Limit Site Visibility in the Content Explorer based on Roles/Users

Can someone point me in the right direction on how or if you can limit site visibility( left hand navigation i.e. //Sites ) in the content explorer based on Roles/Users ?


Even if a user does not have edit rights to a Site, it remains visible to them so they can search its content to add cross-Site links (links from Content Items in one Percussion CM-managed Site to another Percussion CM-managed Site).