An event would not be ideal. What would be a better idea would be to have a wand-like tool where when an admin (level decided by pref) equips it, when they look at a brick, it glows either green (for anyone is allowed to use) or red (for admin only). When an admin uses this want on the brick, it toggles whether this brick is unrestricted to everyone or admin only. Additionally, perhaps have a /command where admins can delete any restricted bricks in existence if they are looking at it with the wand out?
Also will have bottomPrint stuff for the user.