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.
As a general principle, the Quran tells us that, even where an external attack is feared, the common man should not act independently, but should take the matter to the ruler, and then under his guidance take proper counter measures. (4:83).
The Hadith also states that ‘the ruler is a shield, fighting is done under him, and security is attained through him.’
This clearly shows that the decision to do battle and its planning are the tasks of an established government. The common man can play his role as need be under government orders, and not independently.
This Islamic principle shows that there is no room for non-state warfare, which is what we generally call guerilla war. A guerilla war is fought by individual organizations, not by the State. As far as the state is concerned, if it wants to wage a defensive war against any country it has first—in obedience to the Quran—to issue a proper declaration. Only then can it wage a lawful war (8:58). In Islam, there is only ‘declared’ war. Therefore, in accordance with this principle, no proxy war in Islam can be lawful.
Most Islamic actions are governed by certain conditions. The waging of war is also thus subject to certain principles, one being that, even when a defensive war has been declared by the State, it will be aimed only at the combatants. Targeting non-combatants will be unlawful. The Quran enjoins us not to do battle with those who are not at war. Such people have to be dealt with kindly and equitably. But you are free to do battle with those who are fighting against you. (60:8-9)
If, for instance, a Muslim state is at war with a particular nation, and this war is in conformance with Islamic principles, it should still not permit any destructive activities against non-combatants (civilians), as was done on September 11, 2001, in New York and Washington. Similarly in Islamic war, Muslims are not permitted to commit suicidal bombings in order to destroy the enemy. Strapping explosives on to oneself and hurling oneself upon the civilian settlements of even those with whom one is at war, for the purpose of destroying the enemy, and in the process killing oneself deliberately, is totally un-Islamic. This can in no way be termed ‘Shahadah’ (martyrdom). According to Islam we can become martyrs, but we cannot court a martyr’s death deliberately.
taken from: http://www.cpsglobal.org/content/war-state-action