The scholars of Islamic law throughout history have agreed upon five main objectives of Islamic law. They are the preservation of:
1. Human Life
2. The Religion
3. The Mind
4. The Wealth
5. The Family and Honor
Ethically speaking this verse explains Islam's view of the sanctity of life.
…Whoever kills someone whether justly or in corruption, it is as though he had slain all of mankind. And if someone saves someone, it is as if he had saved all of mankind..." (Qur'an 5:32)
…Don't kill yourselves…"(Qur'an 4:29)
Legally speaking the base principle in Islam is in the verse? "…And don't kill people except with right because God has forbidden it"(Qur'an 6:151)
The Prophet (pbuh) taught us that the meaning of "except with right" from the abovementioned is as follows:
1. As a punishment for one who has murdered someone
2. Punishment for a proven case of adultery for one who is or has been married. (The punishment for an unmarried is lashes on the back)
3. Punishment for rape
4. In defense of oneself, family, or property
5. In war which has been waged by the Islamic Government
The following are the circumstances in which killing is not allowed even during a legally declared military Jihad:
Fighting the people of the Book and Non Muslims who sought security.
It is forbidden to fight non-Muslims living under the protection of a Muslim government unless he clearly breaches the covenant of the protection. And as long as he sought security and protection under the Islamic law, his blood and property are protected. God said:
"And if any one of the polytheists seeks your protection, grant him protection so that he may hear the words of God (i.e., the Qur'an). Then deliver him to his place of safety. That is because they are a people who do not know"(Qur'an 10: 6).
Today we have a system of Passports and Visas. In Islamic Law these represent legal pacts between different nations of peaceful passing. Therefore if any Muslim country issues a visa to a non-Muslim then no Muslim can touch a hair on their head (enemy or not). The same ruling goes if a Muslim visits a non-Muslim country (enemy or not) then he has no right to attack them. This ruling also extends to Muslim who is a citizen of a non-Muslim country which is hostile to Islam and the Muslims because by being a citizen he is in a legal agreement with that country which requires allegiance to the laws of that land. The Prophet said:
"Anyone who kills a non-Muslim under legal agreement with the Muslims will not smell the fragrance of Paradise."(Bukhari)
Who is prohibited to be killed in the battlefield?
Such as the elderly, woman, children, mentally challenged, monk or priest, or the sick that are not involved nor participated in the battle via supporting the enemy troops physically. Peasants or ambassadors are not allowed to be killed as well as per the Prophet's orders.