Love Hurts - S1-E21
Question: Piper and Leo switch powers so Piper can heal him. Leo ends up dying but Piper finds the trigger to the healing power after his death. How come she is able to bring him back to life when in later episodes it is revealed that Leo's healing power cannot bring the dead back to life?
Chosen answer: It probably meant that it couldn't bring humans back to life, magical or not. As a Whitelighter, Leo is technically not human because he's already died as a mortal. The only way to heal a Whitelighter from the poison that "kills" them is to be healed with the healing power of a Whitelighter.