From the Express Tribune:
On Monday, US President Barack Obama’s assistant on counterterrorism and homeland security, John Brennan said that they are carried out “in full accordance with the law”.
Speaking at the Woodrow Wilson International Center for Scholars in Washington DC, Brennan said, “there is nothing in international law that bans the use of remotely piloted aircraft for this purpose or that prohibits us from using lethal force against our enemies outside of an active battlefield, at least when the country involved consents or is unable or unwilling to take action against the threat.”