Internalists argue that a person can be liable only to the least harmful means of averting a threat. On this view, liability has an internal necessity constraint (McMahan 2009: 9). Since Victim can avoid harm by using the parachute in Jump, harming Gunman is unnecessary for averting the threat Gunman poses. Thus, Gunman is not liable to defensive harm. In Poison, harming Adversary is unnecessary because it is pointless. Nothing can be done to avert Adversary’s threat to Victim, and so Adversary cannot be liable to defensive harm.