The White House reportedly is developing rules for when to kill terrorists around the world. The world may never see them, given the Obama administration’s inclination toward unnecessary secrecy regarding its national security policy. But the effort itself is a first step toward acknowledging that when the government kills people away from the battlefield, it must stay within formal guidelines based on the rule of law — especially when the life of an American citizen is at stake.

For eight years, the United States has conducted but never formally acknowledged a program to kill terrorists associated with Al Qaeda and the Taliban away from the battlefield in Afghanistan. Using drones, the Central Intelligence Agency has made 320 strikes in Pakistan since 2004, killing 2,560 or more people, including at least 139 civilians, according to the Long War Journal, a Web site that tracks counterterrorism operations. Another 55 strikes took place in Yemen.

Administration officials have never explained in any detail how these targets are chosen. Are they killing people only associated with groups that participated in the Sept. 11 attacks, the limitation imposed by Congress when it authorized military force in 2001? Or are they free to remove any threat to the United States they perceive? Officials insist they go after only actual belligerents covered in the 2001 legislation, but the public and the world have no way of knowing whether these decisions are made ad hoc, or how they would be interpreted by future presidents.

Before the election, when it looked as if Mitt Romney had a chance of winning the White House, administration officials began codifying these rules, according to a recent report in The Times by Scott Shane. Mr. Obama did not want to leave an “amorphous” program to his successor, one official told Mr. Shane anonymously.