The letter called President Uribe's attention to international legal standards that limit the use of lethal force in law enforcement operations. It emphasized that an anti-drug program that authorized the downing of aircraft simply because they fail to observe identification procedures or disregard orders to land would violate these standards.

"Suspect aircraft cannot simply be fired upon as if they were combatants in an armed conflict," said José Miguel Vivanco, executive director of the Americas Division of Human Rights Watch. "While we are deeply concerned about the destructive impact of drug trafficking, we call on the Colombian government to fight trafficking using methods that do not violate human rights."

The U.S. government is reportedly planning to restore a joint program with Colombia aimed at intercepting aircraft suspected of transporting illegal drugs. The program was suspended over two years ago, after the April 2001 downing of a plane transporting an American missionary family in Peru.

In the letter to President Uribe, Human Rights Watch emphasized that international law enforcement standards strictly limit the use of lethal force against fleeing suspects. Unless suspect aircraft actually present a threat of death or serious bodily injury to law enforcement officers or third parties, they cannot be shot down.

Even if "mistakes" could be avoided in the future, the letter stated, the downing of aircraft that pose no imminent threat to human life would still violate international law, no matter what their cargo contained.

Human Rights Watch has previously raised these concerns with the U.S. government. In a letter sent to President George W. Bush in July 2001, for example, Human Rights Watch explained how the use of lethal force in aerial anti-narcotics operations in Peru had violated international law.