There already is a grieving rule.
"
Regarding Griefing
Griefing is when a player finds a way to destroy something they do not have access to. An example of this is destroying any servers spawns or areas the normal player does not have access to edit. Griefing is also forbidden for players with trust or build access on your plot. Having access to build/break doesn't mean you get a free pass to grief.
Lava walling players or anything of the manner that restricts or hinders other players on friendly servers is included and classified as griefing.
Griefing will result in an instant ban with no questions asked."