Does parliamentary supremacy apply in the case of triggering article 50?

UK Supreme Court Hearing On Brexit Case & Trigger Article 50 – EU

Lord Pannick, representing the lead claimant in the Brexit constitutional case, argued that a full act of the British parliament would be required prior to any Brexit scenario moving forward. In other words, before the United Kingdom can trigger Article 50 announce its intentions to leave the European Union, the Parliament must approve a measure to trigger such motion.

“Only an act of parliament can lawfully confer power on the [government] to give notification under article 50 [of the treaty of the European Union]…The law is not altered by a motion in parliament. A motion in parliament cannot effect the legal issue in this case.”

Pannick argued with Lord Neuberger on Wednesday over whether the Brexit vote had seceded power from the parliament to the people, thus negating the need for a parliamentary act, saying “It would be surprising if the referendum act and the referendum had no effect ni law.”

Pannick’s reply: “The 2015 act is entirely neutral on the issue before this court: whether or not a minister has the power to notify [Brussels that the UK intends to leave the EU].”

Dominic Chambers argued for the supremacy of the parliament in all matters of law and stated that if Theresa May acted to trigger article 50 without the consent of parliament, she would be acting unlawfully, as the powers conferred to the UK in the European Union were done so through parliamentary action.

“By triggering article 50 these statutory rights will be nullified and overridden. The absence of parliamentary authorisation for the executive override primary legislation…will be contrary to the doctrine of parliamentary sovereignty and therefore it will acting unlawfull.”

[The Guardian – Ministers would need full act of parliament to trigger Brexit, court told]