Human: What is the name of the Islamic legal principle that Ibn Hajar al-Asqalani used to justify rebellion against a ruler? Assistant: 
The Islamic legal principle that Ibn Hajar al-Asqalani used to justify rebellion against a ruler is the principle of "haraam" (forbidden). Al-Asqalani said that to ignore such a situation is "haraam", and those who cannot revolt inside the caliphate should launch a struggle from outside.