I would agree that all work projects should be approved through the local land manager.
An exception may include a fallen tree making a trail impassable. In that case, it may be much more damaging to turn an entire group around than to remove the offending item on an established right of way. This should be a common sense decision since sometimes it is not practical to turn around.
I've moved a stolen car out of the way then reported it to the local land manager. For stolen/abandoned cars, give a VIN and the best possible vehicle description.
2002 Jeep Liberty Limited 4x4
OME heavy springs
Bilstein front struts and rear shocks
Yokohama Geolander AT-S 245 75r16