"That this House approves Her Majesty's Government's decision of principle to join the European Communities on the basis of the arrangements which have been negotiated."
2. A Member State which decides to withdraw shall notify the European Council of its intention......
The UK government appeared content to proceed on the basis that the referendum was the decision to withdraw. This “will of the people” argument has considerable political leverage even though the UK is a “representative democracy”. Referendums have the potential to impinge on that concept particularly if the legislation authorising the referendum does not, as was the case here, specify clearly what is to be done depending on the outcome. Given the advisory nature of the referendum and the fact that the 2015 Act did not set out specific action, it was for Parliament – as the representative institution – to make the final withdrawal decision. If that is correct then the decision would have to be expressed by Act of Parliament in order for it to have binding legal effect.
The second stage of Article 50 concerns notification of the decision to withdraw. A view was strongly held by the government and by many lawyers that prerogative powers relaying to treaty making (and unmaking) could be used to give the notice to the EU without the need for specific parliamentary authority. This resulted in the legal challenge mounted by Gina Miller and Deir Dos Santos. Their argument was essentially that membership of the EU had given the citizen specific rights and those could only be removed by Parliament and not by the executive using prerogative powers. This was an argument founded on well-established law that the Royal Prerogative, whilst it embraces the making of treaties, does not extend to altering the law or conferring rights upon individuals or depriving individuals of rights which they enjoy in domestic law without the intervention of Parliament – speech of Lord Oliver in J.H. Rayner (Mincing Lane) Ltd v Department of Trade  2 AC 418 – (sometimes referred to as the Tin Council case).
D] Professor Steve Peers (University of Essex), writing on EU Law Analysis (25th January 2017), commented that – “Despite many constitutional lawyers’ criticism of the technicalities of the judgment, in my view it at least fully expresses the traditional spirit of the UK constitution – and Parliament’s historic role in British political life.”
If Labour were to form the next government there would be a European Union Rights and Protection Bill in place of the Conservative Great Repeal Bill. This would ensure there is no detrimental change to workers’ rights, equality law, consumer rights or environmental protections as a result of Brexit.