The book says somewhere (I don't have mine with me at the moment) that one cannot run the bases in reverse order to make a mockery of the game. In that case the runner would be called. However, if the runner heads back to the previous base and he gets tagged, I also have an out. It's up to him and/or his coach to know the situation. If he wanders away, he does so at his own risk.
Consider a variation on this theme. What if R1 rounds second on a caught flyball? Are you saying that he wouldn't be permitted to return to first since he had already acquired second?
Outs are sometimes hard to come by. Don't look a gift horse in the mouth.
