They cite cases in which the courts assumed that an Act of Parliament would be necessary before the UK could repudiate the EU Treaties: Blackburn v AG [1971] 2 All ER 1380, [1971] 1 WLR 1037,
per Denning LJ; Macarthys Ltd v Smith [1979] IRLR 316, [1979] 3 All ER 325
per Lord Denning; R (Shindler) v Chancellor of the Duchy of Lancaster [2016] EWCA 469
per Lord Dyson; Pham v Secretary of
Stater for the Home Department [2015] UKSC 19, [2015] 3 All ER 1015,
per Lord Mance.)