Permissions to mark OR unmark

Instead of only having permissions to mark AND unmark a node, it would seem to be useful to be able to say who can and can't unmark the node as well. This would only make sense for "global" bookmarks. For example, any user could mark a node to be reviewed. This is a global flag so everyone would see that it is currently marked for review.

However, only an editor or admin should be able to unmark the "under review" flag.

I hope this makes sense. If this is already available, I'm sorry. :D