Fis diwethaf, dyfarnodd yr Uchel Lys na chaiff Llywodraeth y DU ddefnyddio uchelfraint y Goron i sbarduno Erthygl 50 o Gytuniad yr Undeb Ewropeaidd, fyddai'n dechrau'r broses o adael yr UE.
Last month, the High Court ruled the UK Government cannot use the Crown Prerogative to trigger Article 50 of the Treaty on European Union, which would begin the process of the UK withdrawing from the EU.