Historically, as during the war with revolutionary France, parliament has suspended habeas corpus to allow for executive detention. More recently the preference has been to pass emergency powers explicitly authorising it. In 1915, Regulation 14B was brought in under powers delegated to the privy council under the Defence of the Realm Act 1914 (DORA), in response to the perceived threat of pro-German collaborators within the populace. Arthur Zadig, of German birth but a naturalised British subject, was one of those so detained. He sought habeas corpus and challenged the very validity of the regulation. DORA contained nothing about detention and those who voted for it could not have envisaged anything as exceptional as Regulation 14B being introduced. R. v. Halliday ex parte Zadig (Halliday being his detention-camp commandant) made its way to the highest court in the land, the judicial committee of the House of Lords, where it was argued in March 1917. The issue was simple: should major changes in the constitution be authorised solely by parliament, or should the executive be allowed to make such changes by delegated legislation? Zadig argued that 14B was ultra vires – in excess of executive power – and that to uphold the validity of the Order in Council which had introduced the regulation would be to undermine the sovereignty of parliament. Five judges in the King's Bench Division – including the recently appointed Mr Justice Atkin – and three in the Court of Appeal had rejected this argument.