(New York) - The US government should immediately clarify its legal rationale for targeted killings, Human Rights Watch said in a letter today to President Barack Obama.

A federal court judge's dismissal of a lawsuit on December 7, 2010, challenging the US government's targeted killing program abroad underscores the urgent need for the Obama administration to publicly explain its policy, Human Rights Watch said. Judge John Bates of the US district court in Washington, DC dismissed the lawsuit on procedural grounds but did not address the merits of the case.

"President Obama should answer the fundamental questions of how his administration determines whether a person may be targeted," said Kenneth Roth, executive director of Human Rights Watch. "Such operations may be lawful under certain circumstances, but absent clear boundaries, they will inevitably violate international law and set a dangerous precedent for abusive regimes around the globe."

The lawsuit, brought by the American Civil Liberties Union and the Center for Constitutional Rights, challenged the US government's decision to authorize the targeted killing of American cleric Anwar al-Awlaki, who is believed to be hiding in Yemen. The US government says al-Awlaki is linked to the Yemen-based al Qaeda in the Arabian Peninsula but has not brought formal charges against him. The lawsuit also sought to have the government disclose the legal standard it uses to place US citizens on alleged government "kill lists."

The Obama administration dramatically expanded the use of targeted killings outside of traditional battlefields following the attacks of September 11, 2001. Many of these killings are conducted by the Central Intelligence Agency through the use of Unmanned Combat Aircraft Systems (drones). The US government asserts that it has authority under international law to use lethal force outside of clearly defined war zones because it is engaged in a global armed conflict with al Qaeda and associated forces.

Human Rights Watch recognizes that the US government has a responsibility to respond to national security threats. The deliberate use of lethal force can be legal in operations involving a combatant on a genuine battlefield, or in a law enforcement action in which the threat to life is imminent and there is no reasonable alternative.

"US government claims that the entire world is a battleground in which the laws of war are applicable undermine the protections of international law," Roth said. "This discredited notion invites the application of lethal force by other countries in situations where the US would strongly object to its use."

Human Rights Watch called on Obama to provide greater clarity on how the US government determines when a targeted killing in an armed conflict situation meets the requirements of distinction and proportionality under the laws of war and the measures it is taking to minimize civilian harm. During armed conflict, only combatants or civilians who are actively participating in hostilities may be lawfully targeted.

Human Rights Watch said that under international human rights law, the use of lethal force is lawful if the targeted individual presents an imminent threat to life and less extreme means, such as capture, are insufficient to address that threat. For strikes outside of conflict zones, the US should fully explain the clear and imminent threat to life that the targeted individual represents and the circumstances that prevented less-than-lethal force from being applied, Human Rights Watch said.

The United States also should provide timely and adequate compensation to all civilian victims of drone strikes or other targeted killings, even if the harm incurred is legally justified, just as it does when US forces inadvertently kill civilians in conflict areas such as Afghanistan or Iraq, Human Rights Watch said.

"Governments' coercive power, especially the awesome power to deprive people of their lives, must be exercised within limits defined by laws that protect human rights," Roth said. "Only by acting in accordance with those limits will the US set an example for the rest of the world."