i would pull all those planted inappropriately

That would just create a larger problem when people can't find the box they're looking for, because they'll spend more time searching, and if the location is delicate that could lead to greater damage. What is your goal? Making sure everyone follows rules? Or is the goal to make sure nothing is damaged in the park? If it's the latter, then never remove a box until the listing is first removed.

Also, is the box in an area where it could cause actual damage? I'd respond to a box that leads to people crushing a delicate alpine zone differently than a box planted in the middle of a forest. One is a technical rule breaking issue and the other is causing actual harm. It's the difference between driving 56 mph in a 55 zone (a violation of state law for which you can be fined) vs someone driving hazardously at 110 mph.