[Racer26]

My interpretation of the way the GDC intends for this game to be played is that defense of this variety is both allowed and encouraged, though I agree the letter of the rule is a bit ambiguous.

Clearly, they don't intend for me to be grabbing, carrying or throwing my opponents BALLs, but I can't see them also meaning to discourage defensive bulldozing of an opponent's BALL. They seem to have tried to go in that direction with the blue box on the POSSESSION rule, but its a bit unclear how 'herding' will be called, both for the purposes of ASSISTs and for the purposes of POSSESSING and opponents BALL.