On Wednesday, Hamas political leader Ismail Haniyeh, one of the chief negotiators for a cease-fire and hostage release deal in Gaza, was killed in his accomodation in Tehran when a bomb detonated remotely. 

His death could well be described as a "targeted killing," something legal experts with the International Committee of the Red Crossdefine as "the intentional and pre-meditated use of lethal force by a state or organized armed group against a specific individual outside their physical custody."

Despite the fact that any authority has yet to claim responsibility, it seems highly likely that the government of Israel was behind the attack. Israel is currently engaged in a military campaign in Gaza, where it says it is fighting against the militant Hamas group and has a long history of targeted killings and a record of (mostly) denying responsibility for such acts.

The current death toll in Gaza is estimated to be almost 40,000. Germany, the European Union, the US and others classify Hamas as a terrorist organization.

'Frustration of terrorism'

According to the 2008 academic book "Targeted Killing in International Law," authored by Nils Melzer, now a law professor,  Israel was likely the first country in the world to acknowledge a policy of targeted killing in 2000. It was seen as a "policy of targeted frustration of terrorism" by the government and was used openly during what is now known as the second Palestinian intifada, or uprising, in 2000.

At the time, Israeli helicopters, gunships and booby traps were used on people in the Palestinian territories that Israel claimed were terrorists. By 2007, 210 such "targets" had been killed, along with 129 innocent bystanders,leading Israeli human rights organisation B'Tselem reported.

Israel is not the only country to employ the practice. Many others — including the US, Russia, Switzerland, Germany and the UK — have also carried out targeted killings. Legal scholars say that since September 11, 2001, targeted killing has become increasingly accepted globally.

Prominent examples include the 2011 killing of al-Qaeda leader Osama bin Ladenby US special forces in Pakistan, and more recent drone strikes in Syria and Lebanon. In 2014, the German political magazine Der Spiegel allegedthat the German military had played an important part in targeted killings of Taliban members in Afghanistan.

How legal is it really?

Targeted killings are often controversial because such assassinations — especially when committed in another nation — are perceived as a violation of a country's sovereignty. But as to whether these sorts of acts are against the law remains unclear.

In 2002, targeted killing became a topic of debate in Israel when an Israeli and Palestinian human rights group tried to prevent it. It took the Israeli Supreme Court five years to come to a decision.

"The government of Israel employs a policy of preventative strikes which cause the death of terrorists," an Israeli judge confirmed in December 2006. "These strikes at times also harm innocent civilians. Does the state thus act illegally?" asked head judge Aharon Barak.

The court's answer? It depends.

"It is decided that it cannot be determined in advance that every targeted killing is prohibited according to customary international law," the judgment concluded. "Just as it cannot be determined in advance that every targeted killing is permissible according to customary international law."

Complex legal frameworks

Legal experts say a number of different questions impact whether a targeted assassination is legal or not. One of the most important is which legal framework the killing is assessed under. Domestic law, certain laws of war, and international humanitarian law are among them.

For example, international humanitarian law, or IHL, is applied in times of conflict and actually allows certain violent acts to be committed during fighting. But even under IHL, the killing could still be questioned if the victim was not directly participating in hostilities at the time they were killed, lawyers have previously argued. 

Other issues include whether the state that committed the killing was an occupying power, whether it could have stopped the target in some other way (such as by detaining the victim), whether there is robust law enforcement in the area that could have intervened instead, and what sort of danger civilians were in.

No red lines?

Human rights organizations often argue that all targeted killings are illegal and have expressed concern that they are becoming too commonplace. Meanwhile governments often see them as a useful tool.

The Israeli government has regularly used the tactic, according to local journalists. "In my reporting, I found that since World War II, Israel has used assassination and targeted killing more than any other country in the West, in many cases endangering the lives of civilians," Israeli investigative journalist Ronen Bergman wrote in the New York Times, in an adaptation out of his 2018 book, "Rise and Kill First: The Secret History of Israel's Targeted Assassinations."

Bergman continued: "But I also discovered a long history of profound — and often rancorous — internal debates over how the state should be preserved. Can a nation use the methods of terrorism? Can it harm innocent civilians in the process? What are the costs? Where is the line?"

Timeline of Israel's significant targeted killings 

1960s: Israel made various attempts to kill Yasser Arafat, former chairman of the Palestine Liberation Organization. These included potentially downing passenger planes he was on and trying to brainwash a Palestinian prisoner into murdering him.

Arafat died in France in 2004, aged 75. His official cause of death was a stroke resulting from a blood disorder. Later on, rumours spread he had in fact been poisoned by Israel but these could never be confirmed, even after an autopsy.

1996: Head bomb-maker for Hamas, Yahya Ayyash, answers a booby-trapped phone which explodes, killing him.

1997: Israeli secret service operatives inject poison into the ear of Khaled Meshal, head of Hamas' political wing, while in Amman, Jordan. The king of Jordan threatens to place the Israeli operatives on trial and pull back on a peace agreement unless an antidote is provided. They do, and Meshal survives.

2000: Israeli helicopters fire missiles at the car of a senior Fatah activist, Hussein Abayat, in his West Bank village. Abayat and two innocent bystanders die. Experts believe this marks the start of Israeli state policy of targeted killings.

2002: Israel drops a bomb on the Gaza home of Hamas military leader Salah Shehade, killing him, his family and 12 neighbours.

2004: An Israeli air strike kills Hamas rocket expert Adnan al-Ghoul and an aid while they are traveling by car in Gaza.

An Israeli helicopter strike kills one of the founders of Hamas, Ahmed Yassin, in Gaza.

Another of Hamas' co-founders, Abdel Aziz Rantisi, is also killed by missiles fired at his car by an Israeli helicopter.

2009: Hamas political leader, Nizar Rayan, is killed by Israeli bombs in Gaza, along with nine members of his family. Hamas' interior minister, Saeed Seyyam, is also killed in an Israeli airstrike.

2010: One of the founders of Hamas' military wing, Mahmoud al-Mabhouh, is killed by Israeli operatives in a Dubai hotel room.

2012: Head of Hamas' military wing, Ahmad Jabari, is killed after an Israeli airstrike on his car in Gaza. Ten other people are also killed.

2023: In December, a drone attack in Damascus, Syria, kills Seyed Razi Mousavi, adviser to the Iranian paramilitary Revolutionary Guard. Israel does not claim the attack.

Edited by: Maren Sass