Len, that is an interesting thought: "Perhaps there are agencies that trust the campers to be responsible." Certainly in the more densely populated areas of California, the prevailing wisdom in the national forests is: "Everything not expressly permitted is forbidden."
And, in fairness, they are sort of forced to adopt that stance -- there are so many people, and so many of them are abusive, that a more lenient attitude would result in wholesale trampling. Several of the forests on the west side of the Sierra are already threadbare due primarily to vehicular damage.
