Rule No. 1: You can kill bystanders without feeling a lot of guilt.
The Koran, as translated by the University of Southern California Muslim Student Association's Compendium of Muslim Texts, generally prohibits the slaying of innocents, as in Verse 33 in Chapter 17 (Isra', The Night Journey, Children of Israel): "Nor take life, which Allah has made sacred, except for just cause."
But the Koran also orders Muslims to resist oppression, as verses 190 and 191 of Chapter 2 (The Cow) instruct: "Fight in the cause of Allah with those who fight with you, but do not transgress limits; for Allah loveth not transgressors. And slay them wherever ye catch them, and turn them out from where they have turned you out, for tumult and oppression are worse than slaughter. ..."
In the typical car bombing, some Islamists say, God will identify those who deserve to die — for example, anyone helping the enemy — and send them to hell. The other victims will go to paradise. "The innocent who is hurt, he won't suffer," Dr. Massari says. "He becomes a martyr himself."
There is one gray area. If you are a Muslim who has sinned, getting killed by a suicide bomber will clean some of your slate for Judgment Day, but precisely where God draws the line between those who go to heaven or hell is not spelled out.
Rule No. 2: You can kill children, too, without needing to feel distress.
True, Islamic texts say it is unlawful to kill children, women, the old and the infirm. In the Sahih Bukhari, a respected collection of sermons and sayings of the Prophet Muhammad, verse 4:52:257 refers to Ghazawat, a battle in which Muhammad took part. "Narrated Abdullah: During some of the Ghazawat of the Prophet a woman was found killed. Allah’s Apostle disapproved the killing of women and children."
But militant Islamists including extremists in Jordan who embrace Al Qaeda's ideology teach recruits that children receive special consideration in death. They are not held accountable for any sins until puberty, and if they are killed in a jihad operation they will go straight to heaven. There, they will instantly age to their late 20s, and enjoy the same access to virgins and other benefits as martyrs receive.
Islamic militants are hardly alone in seeking to rationalize innocent deaths, says John O. Voll, a professor of Islamic history at Georgetown University. "Whether you are talking about leftist radicals here in the 1960s, or the apologies for civilian collateral damage in Iraq that you get from the Pentagon, the argument is that if the action is just, the collateral damage is justifiable," he says.
Rule No. 3: Sometimes, you can single out civilians for killing; bankers are an example.
In principle, nonfighters cannot be targeted in a militant operation, Islamist scholars say. But the list of exceptions is long and growing.
Civilians can be killed in retribution for an enemy attack on Muslim civilians, argue some scholars like the Saudi cleric Abdullah bin Nasser al-Rashid, whose writings and those of other prominent Islamic scholars have been analyzed by the Combating Terrorism Center, a research group at the United States Military Academy at West Point, N.Y.
Shakir al-Abssi, whose Qaeda-minded group, Fatah Al Islam, has been fighting Lebanese soldiers since May 20, says some government officials are fair game. He was sentenced to death in Jordan for helping to organize the slaying of the American diplomat Laurence Foley in 2002, and said in an interview with The New York Times that while he did not specifically choose Mr. Foley to be killed, "Any person that comes to our region with a military, security or political aim, then he is a legitimate target."
Others like Atilla Ahmet, a 42-year-old Briton of Cypriot descent who is awaiting trial in England on terrorism charges, take a broader view. "It would be legitimate to attack banks because they charge interest, and this is in violation of Islamic law," Mr. Ahmet said last year.
Rule No. 4: You cannot kill in the country where you reside unless you were born there. [Ed: see The Covenant of Security]
Militants living in a country that respects the rights of Muslims have something like a peace contract with the country, says Omar Bakri, a radical sheik who moved from London to Lebanon two years ago under pressure from British authorities.
Militants who go to Iraq get a pass as expeditionary warriors. And the Sept. 11, 2001, attacks did not violate this rule since the hijackers came from outside the United States, Mr. Bakri said.
"When I heard about the London bombings, I prayed that no bombers from Britain were involved," he said, fearing immigrants were responsible. As it turned out, the July 7, 2005, attack largely complied with this rule. Three of the four men who set off the bombs had been born in Britain; the fourth moved there from Jamaica as an infant.
Mr. Bakri says he does not condone violence against innocent people anywhere. But some of the several hundred young men who studied Islam with him say they have no such qualms.
"We have a voting system here in Britain, so anyone who is voting for Tony Blair is not a civilian and therefore would be a legitimate target," says Khalid Kelly, an Irish-born Islamic convert who says he studied with Mr. Bakri in London.
Rule No. 5: You can lie or hide your religion if you do this for jihad.
Muslims are instructed by the Koran to be true to their religion. "Therefore stand firm (in the straight Path) as thou art commanded, thou and those who with thee turn (unto Allah), and transgress not (from the Path), for He seeth well all that you do," says verse 112 of Chapter 11 (Hud). Lying is allowed only when it is deemed a necessity, for example when being tortured, or when an innocuous deception serves a good purpose, scholars say.
But some militants appear to shirk this rule to blend in with non-Muslim surroundings or deflect suspicion, says Maj. Gen. Achraf Rifi, the general director of Lebanon's internal security force who oversaw a surveillance last year of a Lebanese man suspected of plotting to blow up the PATH train under the Hudson River.
"We thought the story couldn't be true, especially when we followed this young man," General Rifi said. "He was going out, drinking, chasing girls, drove a red MG." But he says the man, who is now awaiting trial in Lebanon, confessed, and Mr. Rifi recalled that the Sept. 11 hijacker who came from Lebanon frequented discos in Beirut.
Mr. Voll takes a different view of the playboy-turned-militant phenomenon. He says the Sept. 11 hijackers might simply have been "guys who enjoyed a good drink" and that militant leaders may be seeking to do a "post facto scrubbing up of their image" by portraying sins as a ruse.
Rule No. 6. You may need to ask your parents for their consent.
Militant Islamists interpret the Koran and the separate teachings of Muhammad that are known as the Sunna as laying out five criteria to be met by people wanting to be jihadis. They must be Muslim, at least 15 and mature, of sound mind, debt free and have parental permission.
The parental rule is currently waived inside Iraq, where Islamists say it is every Muslim's duty to fight the Americans, Dr. Massari says. It is optional for residents of nearby countries, like Jordan.
In Zarqa, Jordan, the 24-year-old Abu Ibrahim says he is waiting for another chance to be a jihadi after Syrian officials caught him in the fall heading to Iraq. He is taking the parental rule one step further, he said. His family is arranging for him to marry, and he feels obligated to disclose his jihad plans to any potential bride.
"I will inform my future wife of course about my plans, and I hope that, God willing, she might join me," he said.