The legal grounds on which the UK Government is maintaining its right to invoke the article 50 process for withdrawing from the European Union without authorisation by Parliament, have been published following a successful application to the High Court by a group of challengers.

Mr Justice Cranston ruled in response to an application by the People's Challenge organisation that parties to the case should not be prohibited from publishing the defendant’s or their own detailed grounds, since "against the background of the principle of open justice, it is difficult to see a justification for restricting publication of documents which are generally available under the Rules".

The applicants and others have brought a case seeking to establish that article 50, which allows a member state to withdraw from the EU "in accordance with its own constitutional requirements", can be legally invoked only on the authority of Parliament, because it would otherwise go against the rights and duties enacted in the European Communities Act 1972. The Government asserts that giving notice under article 50 is a matter that falls within its prerogative powers.

A hearing has been set down for October. Opposing the application for disclosure, the Government argued that a case management order made in July meant that all court papers had to remain confidential. However the court ruled last night that both the skeleton arguments and the detailed grounds on both sides may be published, with redactions if necessary to protect parties' identities or addresses.

The applicants argue that:

  • the prerogative is a residual power, which has been implicitly abrogated by domestic statutory provisions in this field, and the executive can neither “decide” that the UK should withdraw from the EU nor lawfully “notify” the European Council of any such decision without Parliament’s statutory authority;
  • alternatively, any prerogative power that subsists, does not extend to modifying, abrogating or removing fundamental rights, in particular citizenship rights;
  • alternatively, if neither of the above is correct, it would be an abuse of that prerogative power for the Secretary
  • of State to decide that the UK will leave the EU and/or to notify that decision to the European Council under article 50 without Parliament’s statutory authorisation to do so.

In response, the Government's case is that:

  • notification under article 50 is "an administrative act on the international law plane" which cannot be complained about in the domestic courts;
  • use of the prerogative would be constitutionally proper, as it was understood that the Government would give effect to the result of the referendum;
  • the decision to withdraw is non-justiciable, being "a matter of the highest policy reserved to the Crown", as, equally, is the appropriate point to begin the procedure required by article 50(2);
  • the relief sought, which would compel the Secretary of State to introduce legislation to Parliament, is "constitutionally impermissible";
  • to the extent that the claim is justiciable, the exercise ot the prerogative power is consistemt with domestic constitutional law; and 
  • the lawful use of the prerogative is not impacted by the devolution legislation, the conduct of foreign affairs being a reserved matter, and "Whilst there are provisions in the devolution legislation that envisage the application of EU law, they add nothing to the lead claimant's case."

Click here for the applicants' submissions.

Click here for the Government submissions.