Some U.S. predator drone attacks may constitute war crimes and all such killings can encourage others to flout human rights standards, a U.N. investigator said.

Defending armed drone use by calling them a valid response to the Sept. 11, 2011, terrorist attacks is unjustifiable, Christof Heyns, U.N. special rapporteur on extrajudicial, summary or arbitrary executions, told a U.N. Human Rights Council conference in Geneva, Switzerland, after Russia and China issued a joint statement to the council condemning drone attacks.

The CIA's use of armed drones in places like Pakistan and Yemen began under President George W. Bush but has grown dramatically under President Barack Obama.

New technologies that improve remote drone operators' ability to engage easily in combat in far-flung regions has led to growing diplomatic and non-governmental concerns about civilian casualties and about other countries also acquiring drones, The New York Times reported.

Some countries "find targeted killings immensely attractive," said Heyns, a South African human-rights law professor. "Others may do so in future."

Current drone practices "weaken the rule of law," he said. "Killings may be lawful in an armed conflict [such as Afghanistan], but many targeted killings take place far from areas where it's recognized as being an armed conflict..."

No shit, Sherlock.