Taken from: Dar Al-Ifta:The Conditions and the Rulings for Jihad
1- The nobility of purpose, meaning that no personal interests or private gains should be the aim behind which Jihad is being waged.
2- Never Transgress. The Holy Quran says: " Fight in the way of Allah those who fight you but do not transgress. Indeed. Allah does not like transgressors." (2:190)
3- Fighting should be only against warriors not defenseless civilians who are not in the battlefield and are not equipped or trained to engage in combat.
4- The killing or harming of women and children is strictly prohibited. Al-Bukhari and Muslim reported through Abdullah ibn Umar (may Allah be pleased with them both) that a woman was found dead in one of the battles fought by the Prophet (pbuh); thereupon he condemned killing women and children.
Another phrasing of the hadith states: "The Messenger of Allah (pbuh) forbade killing women and children." Imam al-Nawawi said: "There is a scholarly consensus on putting this hadith in practice as long as the women and children do not fight [the Muslims]. If they do, the majority of scholars maintain that they should be killed." [Sharh Muslim 12/48].
5- Preserving the lives of captives and treating them humanely.
6- Preserving the environment which includes the prohibition on killing animals or cutting trees or destroying harvest or polluting rivers or wells or demolishing houses.
7- Preserving religious freedom for worshippers in their homes, churches or synagogues.
8- Killing and attacking people by surprise is prohibited. Abu Hurairra, may Allah be pleased with him, narrated that the Messenger of Allah (peace and blessings be upon him) said: "A believer is not to kill [others]. Faith is a deterrent to killing." Ibn al-Athir said: "Killing [here] means taking others by surprise and killing them while they are unprepared." [Al-Nihaya fi Gharib al-Hadith wa al-Athar 3/775].
The hadith means that faith is a deterrent to attacking others suddenly while they are unprepared. The Prophets' words: "A believer is not to attack [others] by surprise" is a clear prohibition against deception in combat.
9- Permission to enter a country is considered a non-verbal security agreement not to cause corruption in the host country. Imam al-Khurqi said in his Mukhtasr: "Whoever enters enemy lands in safety is not allowed to cheat them of their money." Commenting on this statement, Ibn Qudama said that it is prohibited to betray them [non-Muslims in non-Muslim countries] because there is an unspoken covenant to enter in safety on the condition that the person who seeks permission to enter a foreign country does not betray or oppress them.
So whoever enters our lands in safety and betrays us violates this security agreement. This is prohibited because it involves treachery which is forbidden in our religion." [Al-Mughni 9/237].
10- The enemy must be from among those whom Muslims are permitted to fight as compared to the enemy with whom Muslims have a truce. It is impermissible to attack the enemy under the cover of night because it is a violation of the security pact between them in terms of lives, wealth, and honor.
11- It is impermissible to use human shields save in a state of war and under specific conditions detailed by jurists. [Bahr Ra`iq 80\5, Hashiyat ibn 'Abn Abdin 223\3, Rawdat al Talibin 239\10, Mughnial Muhtaj 223\4, Mughni ibn Qudama 449\8, 386/10].
12- Cease the fight immediately once your enemy stops as the Holy Quran says: "But if they cease, then there is to be no aggression except against the oppressors." (2:193)