Question:
What is the ruling on attacking a non-Muslim in Muslim lands by beating or killing them, even if it is due to corruption or immorality they are committing?
Answer:
It is not permissible to attack a non-Muslim if they have entered Muslim lands under a covenant of security (peace/visa/agreement), because they are under the protection of the Muslims. It is impermissible to betray the protection guaranteed by Muslims, and it is not permissible to attack them as long as they are inside Muslim lands under a known security agreement and system.
This is because Allah, the Glorified and Exalted, has commanded us to fulfill covenants. He, the Exalted, said: “And if anyone of the Mushrikûn (polytheists, idolaters, pagans, disbelievers in the Oneness of Allâh) seeks your protection, then grant him protection so that he may hear the Word of Allâh (the Qur’ân), and then escort him to where he can be secure.” [Al-Tawbah: 6].
As for if they commit something that warrants punishment, the one who handles that is the ruler (authorities). It is not permissible for individual citizens to punish them, as this leads to chaos and aggression. However, if someone commits an act that violates the religion of the Muslims or harms them, the matter should be raised to the ruler (authorities) so that they may handle the penalization of this offender.