Scholarly consensus holds that a law quoted in Demosthenes (23.53) permitted one to kill a highway robber who had lain in ambush and attacked one on a road. But the relevant phrase says nothing explicit about ambush. Modern interpretation derives from Harpocration and other ancient authorities. It is argued here that they were mistaken and that the phrase referred to those who inadvertently killed a fellow traveler while overtaking on a road.' The new interpretation may offer another way to think about the encounter between Oedipus and Laius.