I am far from a mechanical engineer (but I did sleep at a holiday inn express once), but ABS and off road should not be said in the same breath. The down side with ABS and off highway driving or even on gravel roads is that it will never allow (unless not working) the wheel to lock up. If you are in a sliding situation and you need the wheel to lock in order to grab the hill, gravel, and mud - whatever it may be you will be in major trouble in very short order.
I have driven cars, vans and 4x4 just on gravel roads down hill and have had to do some very fun driving when the ABS works as designed and you do nothing but gain speed into a hair pin turn with a cliff on one side and a mountain on the other.
So as to my opinion, not the opinion of this board or any government agency
I think that ABS should be a selectable item on all vehicles just like passenger airbags on pickup trucks.
Or you should have the option to be able to install a cut off switch without voiding the factory warranty.
But again, I am not an engineer and I am sure someone will explain why I don't have a clue what I am talking about.