Targeted killing with drones and other methods fall into two legal categories: (1) assassination or execution conducted in zones in which the United States is not involved in organized battlefield combat, such as in Pakistan, Yemen, Somalia, Libya and Syria; and (2) attacks by drones in support of U.S. troops in Afghanistan and Iraq.

1. Non-battlefield targeted killing – Targeted killings violate human rights enshrined in the Universal Declaration of Human Rights (UDHR), which is part of customary international law. The UDHR guarantees everyone the right to life, due process, and privacy. All of these rights are violated in the process of assassination by drones and other methods. The UDHR was codified into two binding covenants, including the International Covenant on Civil and Political Rights (ICCPR). The U.S. obligated itself to protect those rights when it ratified the ICCPR in 1992.

The ICCPR spells out the legal obligations of states parties. However, in spite of having ratified the ICCPR, in the case of targeted drone attacks, the U.S. has ignored ICCPR rules and acted illegitimately in taking on the roles of investigator, prosecutor, judge, jury and executioner of suspected terrorists.

The U.N. Human Rights Committee, charged with monitoring whether states parties are living up to their obligations under the ICCPR, said in 2014 it was concerned about the U.S. practice of targeted killing with drones.  It focused on the lack “of legal justification for specific attacks, and the lack of accountability for the loss of life resulting from such attacks.” 

The breach of international law occasioned by drone killing is not excused by the Authorization for the Use of Military Force (AUMF), which Congress passed in 2001. The AUMF authorized the president “to use all necessary and appropriate force” against those who planned and aided the September 11 attacks. Pursuant to the AUMF, the United States invaded and occupied Afghanistan, acting as if the AUMF was in fact international law. The U.S. also invaded and occupied Iraq pursuant to the 2002 AUMF, which said, “The President is authorized to use the Armed Forces of the United States as he determines to be necessary and appropriate in order to . . . defend the national security of the United States against the continuing threat posed by Iraq.” But Iraq did not pose a threat to the U.S. The Bush administration falsely claimed Saddam Hussein had weapons of mass destruction and ties to al Qaeda.

Those invasions and occupations violated the United Nations Charter, as noted by Jeanne Mirer, a civil and human rights lawyer and president of the International Association of Democratic lawyers, in the essential reference Drones and Targeted Killing: Legal, Moral, and Geopolitical Issues. Mirer wrote:

With respect to Afghanistan…”no U.N. body, either before or after the U.S. invasion of Afghanistan passed a resolution stating that the U.S. invasion of Afghanistan was legal...the invasion of Afghanistan was in fact, illegal.”  Heads of state who engineered the invasion, she says, should be “held to account” for waging a war of aggression.

The U.S. invasion of Iraq, Mirer wrote, was an even greater assault against international law since “no one operating on Iraqi soil ever attacked anything or anyone in the United States…” Therefore the U.S. could not claim lawful self-defense under the U.N. Charter.

“This [Iraq] was a war,” wrote Rashid Khalidi in Resurrecting Empire, ”fought firstly to demonstrate that it was possible to free the United States from subordination to international law or the U.N. Charter…”

2. Targeted killing on the battlefield - Mirer wrote in Drones and Targeted Killing that the use of weaponized drones in Afghanistan and Iraq is illegal under international law because these wars themselves are illegal, violating the U.N. Charter.

Speaking in general terms about the legality of drone attacks, she cited the 2010 U.N. report, Study on Targeted Killing, which says:

“Targeted killing is only lawful when the target is a ‘combatant’ or ‘fighter’ or, in the case of a civilian, only for such time as the person ‘directly participates in hostilities.’  In addition, the killing must be militarily necessary, the use of force must be proportionate so that any anticipated military advantage is considered in light of the expected harm to civilians in the vicinity, and everything feasible must be done to prevent mistakes and minimize harm to civilians.”

However, in evaluating the legality of drone attacks in “combat” zones, one must take into account the unique and extraordinary power of surveillance on which drone killing is based.

Drone operators observe general populations when they search for combatants and combat situations involving troops requiring air support.  The drone operators look for suspicious people who may be getting ready to attack or provide support to an enemy.  This is particularly true when combat is underway in and around heavily populated areas. Thus there is drone tracking of ever increasing numbers of people for attack, many of whom are non-combatants.

In his perceptive book, A Theory of the Drone, Gregoire Chamayou wrote that the ability of weaponized drones to circle for long periods of time leads to “militarized manhunting”:

“It is not so much a matter of responding to actual attacks but rather of preventing the development of emerging threats by the early elimination of the potential agents - ‘to detect, deter, disrupt, detain or destroy networks before they can harm’ and to do this in the absence of any direct, imminent threat.

“The political rationale that underlies this type of practice is that of social defense.  Its classic instrument is the security measure, which is ‘not designed to punish but only to preserve society from the danger presented by the presence of dangerous beings in its midst.’  In the logic of this security, based on the preventive elimination of dangerous individuals, ‘warfare’ takes the form of vast campaigns of extra-judicial executions.  The names given to the drones -- Predators (birds of prey) and Reapers (angels of death) -- are certainly well chosen.”

This section on legality of drone war was edited by Marjorie Cohn, professor emerita at Thomas Jefferson School of Law, former president of the National Lawyers Guild and on the advisory board of Veterans for Peace.  Her books include: Cowboy Republic: Six Ways the Bush Gang Has Defied the Law; The United States and Torture; Interrogation, Incarceration and Abuse; and Drones and Targeted Killing: Legal, Moral and Geopolitical Issues.

A final note: Jeanne Mirer says that: “U.S. leaders, in the name of fighting ‘terrorism’ are acting criminally, and are subject to prosecution in the International Criminal Court.”