Mr Paines was appointed as Law Commissioner with responsibility for public law on 18 November 2013. On 19 July 2018 he was reappointed for a further five years.  He was formerly a leading silk in EU and public law. He sits as a Deputy High Court Judge in the Administrative Court, a Deputy Judge of the Upper Tribunal (Administrative Appeals Chamber) and the First-tier Tribunal (Tax Chamber) and a Recorder in the Crown Court. He is also a member of the Bar of Northern Ireland.