The purpose of this panel is not to rehash doctrinal controversies around the Article 50 Miller decision of the UK Supreme Court. Instead it will move the academic debate forward by considering some fundamental questions about prerogative powers in light not only of that case but also comparative judicial treatment of non-statutory executive powers (‘NSPs‘), including the so-called ‘third source‘ powers. It will ask in particular: can statute shrink the scope of the prerogative or merely render particular exercises of it unlawful? Does statute replacing a prerogative abolish the latter or merely place it in (temporary) abeyance? Is the prerogative best conceived of as a broad residual power or a bundle of discrete powers – and how does that compare with NSPs in other jurisdictions, such as the US, Israel and France? How does UK case-law determining the existence and scope of particular prerogative powers compare to that identifying and delineating NSPs elsewhere?