There has been a great deal written over the last week discussing the procedure that should be followed for withdrawing from the European Union. Article 50 of the Treaty on the European Union (often referred to as the Lisbon Treaty) states that: “any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.”
This raises the vexing question of what the UK’s archaic, uncodified and unsettled constitution requires in order for there to be a ‘decision’ to withdraw from the EU. Adam Tucker, of Liverpool Law School, provides a useful summary of the positions espoused by various academics over the last few days here, before going on to make his own contribution to the debate.
There is disagreement amongst constitutional lawyers whether “the decision to withdraw is within the government’s inherent prerogative power to conduct foreign affairs” or whether an Act of Parliament is required to give effect to the outcome of the referendum. The possibility that an Act of Parliament may be required has led some to suggest that the Westminster Parliament could block Brexit. If primary legislation is necessary, this would also raise the question of whether a legislative consent motion is required from the Scottish Parliament (previously addressed here on this blog and here and here elsewhere).
Taking a step back from all of the constitutional conjecture, it is worth considering what can actually be done if one feels that the wrong course of action has been adopted. An aggrieved member of the public could seek to judicially review the actions of the Prime Minister if they feel that he has acted ultra vires (i.e. acted beyond his powers) by invoking Article 50 without authorisation from an Act of Parliament. Whilst this may be technically possible, it seems incredibly unlikely that a court would accept an invitation to adjudicate on the issue.
Given that there has been a clear and decisive decision from the electorate that the UK should leave the EU, it would be incredibly controversial for any court to interfere with this decision on the basis of a perceived procedural flaw in the withdrawal process. As noted by the late Lord Bingham in Countryside Alliance v Attorney General  UKHL 52:
“The democratic process is liable to be subverted if, on a question of moral and political judgement, opponents of the Act achieve through the courts what they could not achieve in Parliament". 
Given the UK's tradition of political constitutionalism, the courts are generally reticent to get involved in issues of political judgement. As John Griffith, who laid the foundation for the idea of a political constitution, noted:
‘...it is not possible to argue that something in Britain’s political constitution is ‘unconstitutional’, only that it is ‘politically unwise or undesirable’’ (J Griffith ‘The Brave New World of Sir John Laws’ (2000) 63 Modern Law Review 156 at 175).
Many of us may feel that Brexit is politically unwise or undesirable and may wish that Parliament or the courts could reverse the result. However, the democratically elected Parliament (by passing the European Union Referendum Act 2015) decided to put the question of whether the UK should be a member of the EU to the electorate. The electorate has now made their decision. In such circumstances, neither Parliament nor the courts can feasibly interfere with the result.