There have been multiple civilian deaths as a result of the use of such drones and the committee heard there are concerns inside and outside the US government that drone attacks violate human rights standards and may constitute extra judicial execution.

She sat down but soon left the room, allowing the door to slam behind her.   The committee went on to hear that while the US has more than 7,000 UAVs and more on order, there is still no legal framework for the operation of this new technology.   It's widely suspected the CIA operates a fleet of drones in Pakistan and Afghanistan which they use for targeting Taliban and al-Qaeda leaders. 

There have been multiple civilian deaths as a result of the use of such drones and the committee heard there are concerns inside and outside the US government that drone attacks violate human rights standards and may constitute extra judicial execution. 

Professor Kenneth Anderson from the Washington College of Law at American University told the hearing:

The long-term effect of that, given that there are not necessarily statutes of limitations, could be the problem of CIA officers or for that matter military officers or their lawyers, being called up in front of international tribunals or courts in Spain or some place that say you've engaged in extra judicial execution or simple murder and we're going to investigate and indict. 

The problem, says Professor Anderson, is that administration lawyers haven't justified publically the use of drones, because the administration itself is reluctant to admit drone attacks in places like Pakistan and Afghanistan.

Although nobody in the world doubts what's going on in Pakistan, it's kind of hard for the lawyer to step up and say 'by the way what we're doing is legal and here's why' and give a whole series of reasons and say, 'by the way, we're not admitting that we're actually doing any of this stuff'. It's very hard for the lawyer to get out in front of the client when the client itself has not actually formally stood up and said 'this is what we're doing'.

He says what makes it more difficult is that though the CIA has taken on drone attacks on the Afghan/Pakistan border, it's not doing it as a genuinely covert operation but as an operation that is denied by the administration.

Tuesday's gathering was the opening session of congress's investigation into the use of UAVs.

There will be other meetings like this on Capitol Hill and at them the debate into the use of such drones is likely to continue.