Without question, drones have become the U.S. weapon of choice in the fight against terrorism. Counterterrorism officials say they've come to rely on the pilotless aircraft for their surveillance capability and what officials say is precision targeting. That reliance has led to greater use in the past couple of years, especially in Pakistan and Yemen.
John Bellinger, a State Department legal adviser during the George W. Bush administration, says there are increasing concerns about the frequency of drone attacks.
"We have seen the Obama administration growing more sensitive to the concern that they themselves may be accused of violating international law and more concerned about use by other countries," he says.
The U.S. leads the rest of the world in the development and procurement of drones, but some 60 other nations also have some version of this new weapon. In a speech laying out the administration's justification for drone strikes, U.S. counterterrorism chief John Brennan made it clear the administration is considering how other countries may use drones in the future.
"President Obama and those of us on his national security team are very mindful that as our nation uses this technology, we are establishing precedents that other nations may follow," Brennan said. "If we want other nations to use these technologies responsibly, we must use them responsibly."
Brennan said the administration has determined it can conduct targeted drone strikes against suspected terrorists in order to prevent attacks on the U.S. and to save American lives, and he said there was nothing in international law that bans this. But Bellinger, now a partner at the law firm Arnold & Porter, says it doesn't matter what technology is involved, whether it's a drone or bullet, virtually no other country in the world buys into the U.S. rationale.
"This looks a lot like an assassination; the U.S. firmly believes that it is not — that this is a military action in self-defense against someone," he said. "But the human rights community is growing increasingly concerned about what they call targeted killings of particular individuals."
Bellinger says that at the moment, there is no treaty on drones or targeted killings of individuals in other countries.
Tom Parker, policy director for terrorism and counterterrorism at Amnesty international, says the U.S. needs to be careful because its rationale for the use of drones could be abused by others. For example, the Chinese could use it to go after people it considers a national security threat — maybe Uighur or Tibetan activists living in a third country, he says.
There is "absolutely nothing stopping them from using the same justification," he said. "And, of course, terrorism is often in the eye of the beholder. You're going to see states use this justification to carry out attacks on human rights activists and political opponents."
Kenneth Anderson, a professor at American University law school, and a fellow at the Hoover Institution, agrees the U.S. does need to be careful, and that's why the Obama administration has been carefully stating its policy.
"The United States has never said that all bets are off, you can do whatever you like, or cross these borders as long as you call it a terrorist threat,' " he said.
And, Anderson says, the U.S. didn't lay out what it sees as a rule of international law on the assumption that other countries will abuse that law.
"Instead, what you have to be willing to do is say, 'Come on, that's not a terrorist threat at all; you just want to go after that dissident,' " he says. "And I think that winds up being an important limiting principle for the United States that would put a bound on its conduct but also on others people's conduct as well."
At least that's the hope, Anderson says, for drones and this new type of warfare.