There is a possibility of a new legal challenge to the tech giants. Early last year, an unknown American law student published a scholarly article in a distinguished journal. Lina Khan argued that competition law – known in the United States as anti-trust law – could be used to rein in the activities of huge enterprises like Amazon. Other lawyers disagree with her reasoning - but the Federal Trade Commission is assessing the arguments. Joshua Rozenberg sounds out opinions in the United States. Also this week: should offences committed in childhood mean a criminal record for life?