20An appeal against a determination of a devolution issue by the Inner House of the Court of Session on a reference under paragraph 15 or 16 shall lie to the Judicial Committee.
21An appeal against a determination of a devolution issue by—
(a)a court of two or more judges of the High Court of Justiciary (whether in the ordinary course of proceedings or on a reference under paragraph 17), or
(b)a court of three or more judges of the Court of Session from which there is no appeal to the House of Lords,
shall lie to the Judicial Committee, but only with leave of the court concerned or, failing such leave, with special leave of the Judicial Committee.