Islam does give permission to do battle. But such permission is given only in the case of an attack by opponents in spite of the policy of avoidance being followed by the Muslims, thus creating a situation where self-defense is required. The Quran has this to say: “Permission to take up arms is hereby given to those who are attacked because they have been wronged” (22:38). At another place the Quran gives a valid reason for fighting: “They were the first to attack you” (9:13).
This shows that according to the teachings of Islam, war is to be waged not against the enemy but against the aggressor. If Muslims hold someone to be their enemy, that does not give them the right to attack him. The one and only right given to them is to convey the peaceful message of Islam. Islam permits defensive fighting against violent aggression, but only when all efforts at avoidance and reconciliation have failed. The practical example of the Prophet Muhammad provides an incontrovertible proof of the value of this policy.
In Islam, war is not the prerogative of the individual but of an established government. Only an established government can declare war. In other words, individuals can pray on their own, but they cannot wage wars of their own accord. Only when a war is declared by the ruling government, can the public join in and support it, and not before that. Islam does not sanction individual actions on this issue. Therefore no Non-Governmental Organization or NGO can declare a war.