The Supreme Court has allowed Gerry Adams’s appeal against his 1975 convictions for escaping from lawful custody. When a court quashes a conviction 45 years later, one might imagine that new evidence must have come to light. Not this time: the case turned on a question of law. The Supreme Court ruled that Mr Adams had not been lawfully detained at all, hence his “escape” was not from lawful custody. As Prof Richard Ekins and Sir Stephen Laws set out, this ruling opens the door for Mr Adams, and for others, to bring proceedings against the government for compensation for false imprisonment. It also poses a very serious challenge to the ordinary functioning of government.