The law permits sport to be violent. In almost every other context, law prohibits or heavily regulates activities that regularly produce serious injury. In contact sport, serious injury is an inherent feature. This lecture examines how that legal permission operates, what maintains it, and what happens when it breaks down. It maps three overlapping legal layers: internal sporting regulation, civil liability through the modified negligence standard, and criminal law at the threshold where sporting violence becomes a matter for prosecution. The concussion and cumulative harm evidence has fundamentally changed the landscape — risks that were not disclosed because they were not understood are now documented and attributable.