This is an issue that can be decided by the Muslim ruler who tells us who is an enemy of Islam and who is a kafir with pledge or with permission to live among us etc.

Individuals don’t have the right to go around selecting people and killing them. Such barbaric acts are not from islam.

What is the concept of wajib up qatal? How is it ok to kill someone and who are we to decide if the person is good or bad and deserves to die?