On 26 January 2017, the Government published its European Union (Notification of Withdrawal) Bill (the "Bill") to empower the Prime Minister to notify the EU, under Article 50 of the Treaty on the European Union, of the United Kingdom's intention to withdraw from the EU (otherwise known as "triggering Article 50").

The passing of the Bill will be the first formal step in the Brexit process since the EU Referendum on 23 June 2016. The Government hopes to get the Bill through Parliament in time to meets its self-imposed deadline of 31 March 2016 for triggering Article 50.

The Bill is the Government's response to the Supreme Court's judgment in R (Miller) v Secretary of State for Exiting the European Union, handed down on 24 January 2017, where the Court ruled, by a majority of eight to three, that the Government must be empowered by an Act of Parliament before it can lawfully trigger Article 50 – you can read our blog on that decision here.

In this blog, we consider the Bill's passage through Parliament, whether it is enough to meet the requirements set out in the Supreme Court's judgment in Miller and a few outstanding questions, including the future role of Parliament and the devolved administrations in the Brexit process once the Bill is passed and whether Article 50 can be revoked.

Short and sweet?

As the Supreme Court noted in its judgment, "there is no equivalence between the constitutional importance of a statute… and its length or complexity". And so it has proved. Notwithstanding its "momentous significance", the Government has drafted the Bill so tightly that its single operative clause is only 52 words long.

Power to notify withdrawal from the E

(1) The Prime Minister may notify, under Article 50(2) of the Treaty on European Union, the United Kingdom’s intention to withdraw from the EU.

(2) This section has effect despite any provision made by or under the European Communities Act 1972 or any other enactment.

The reason for this terse legislative drafting is clear: the Government has sought to make the Bill as straightforward as possible to give it the best chance of passing through both Houses of Parliament as quickly as possible, and with minimal amendment. The Government has also indicated that it intends to ask Parliament to fast-track the Bill's passage.

The fate of the Bill, and the likelihood of it passing through Parliament in time to meet the end of March deadline, will largely depend on whether the myriad amendments already (and still yet to be) proposed can be moved for debate in the House of Commons, notwithstanding the Government's best efforts to prevent this from happening. Indeed, the Government's concerns that the Bill would be subject to a febrile reception in Parliament appear to have been justified. As at 27 January, 96 new clauses for insertion into the Bill have been tabled, including 58 relating to parliamentary scrutiny of the wider process for the UK's withdrawal from the EU, as well as numerous amendments to the Bill's existing clauses.

The Bill will have its Second Reading, the first chance for MPs to debate the Bill as a whole, on 31 January and 1 February 2017. Amendments cannot be formally proposed at this stage, but there is likely to be a vote on whether the Bill should be allowed to proceed to the next stage. If that vote passes, the Bill will be considered by a Committee of the Whole House on 6 to 8 February, where amendments will be tabled, discussed and voted on. Once agreed, the Bill will have its Third Reading, also scheduled for 8 February, where MPs will vote on whether to approve the Bill and send it to the House of Lords.

Whether a proposed amendment to a bill can be moved for debate in the House of Commons is determined in accordance with Standing Order No. 65, which provides that MPs have the power to make amendments to a bill "as they think fit, provided they be relevant to the subject matter of the bill". Relevance is usually referred to as the "scope" of the bill, as indicated by the bill's "long title". Amendments determined to be outside the scope of the bill are ruled "out of order" and cannot be moved for debate.

It is therefore significant that the Government has tightly limited the long title of the Bill to one specific purpose, namely giving the Prime Minister the power to notify under Article 50. Whether a specific amendment is within the scope of the Bill will be decided by the Deputy Speaker, Mr Lindsay Hoyle MP, during the Committee Stage. This decision is at Mr Lindsay's absolute discretion and there is no right to appeal.

Never was so much riding on so few words

Although Bill is short, its clauses are nonetheless significant.

Clause 1(1): has the UK decided to leave yet?

The Supreme Court held that an Act of Parliament was needed to authorise both the decision to withdraw from the EU and the giving of notice of that decision under Article 50 (see, in particular, paragraphs 81, 120-124 and 132). However, the Bill as drafted appears only to deal with the second of these, namely the notification of the UK's decision to leave the EU by the Prime Minister, but not whether or not the UK has already decided to leave.

The Government may argue that a combination of the EU Referendum result itself, the Government's commitment to give effect to that result, and Parliament's resolution in December 2016 to respect the wishes of the UK as expressed in the EU Referendum and in favour of the 31 March 2017 deadline, together amount to a "decision".

However, the Supreme Court ruled that the legal effect of a referendum must depend on the terms of the statute that authorises it and where, as in the case of the EU Referendum, the implementation of a referendum result requires a change in the law that is not provided for in the statute authorising the referendum, such change "must be made in the only way in which the UK constitution permits, namely through Parliamentary legislation". In other words, unless and until acted upon by Parliament, the force of the EU Referendum is political rather than legal.

The Bill does not expressly declare that the UK has decided to leave the EU. In addition, clause 1(1) of the Bill is drafted so as to give the Prime Minister discretion, rather than imposing an obligation, to trigger Article 50 (denoted by the use of the word "may", not "shall").

The Government has no doubt sought to do the minimum needed to allow it to begin the Brexit process. Arguably they have achieved this, as a Bill that (once enacted) empowers the Prime Minister to notify a decision by the UK to leave the EU could be said implicitly to authorise the decision being so notified. However, given that the Bill only gives the Prime Minister a discretion to notify, it could be argued that the Bill, if passed in its current form, does not itself go far enough so as to amount to a "decision" by the UK to leave the EU, as the Prime Minister would be free to choose not to exercise her power to notify under the Bill at all.

The legal effect of the Bill would be more certain if this issue was resolved during the parliamentary process. However, the Government may be reluctant to do so – without significant pressure – because of the risk that introducing an amendment to that effect could be hijacked.

Clause 1(2): a constitutional belt and braces

The principle of parliamentary sovereignty dictates that where there is a conflict between two Acts of Parliament, the later Act takes repeal the earlier one, as Parliament cannot bind itself (known as the rule of "implied repeal").

This implied repeal rule might appear to make clause 1(2) of the Bill redundant, as it states that its provisions have effect despite any earlier provisions to the contrary. On the contrary, this provision was most likely inserted into the Bill by Government lawyers in order to limit the risk that the validity of the Bill could be challenged in the courts on the basis of a hitherto untested constitutional principle.

In Thoburn v Sunderland City Council, Lord Justice Laws suggested that the UK constitution recognised a "hierarchy of Acts of Parliament" and that "constitutional statutes" were immune from implied repeal. This means that Parliament could only repeal or abrogate constitutional statutes expressly, such that the courts are satisfied "that the legislature's actual – not imputed, constructive or presumed – intention was to affect the repeal or abrogation".

Since Thoburn, the courts have repeatedly endorsed this principle and often cite the European Communities Act 1972, which gives domestic legal effect to the UK's membership of the EU, as the archetypal constitutional statute. Indeed, the Supreme Court in Miller recognised that the 1972 Act "has constitutional character" and that EU law rights under the 1972 Act cannot be "implicitly displaced by mere enactment of legislation which is inconsistent with it".

The purpose of clause 1(2) therefore appears to be to make clear that, by enacting the Bill, Parliament is squarely confronting the effect of the Bill's provisions on the 1972 Act and other constitutional enactments, including the changes to domestic law that will result from the triggering of Article 50 so as to comply with the principles set out in Thoburn.

The end of the beginning of Brexit

The passage of the Bill through Parliament and the Prime Minister's subsequent notification under Article 50 will undoubtedly be historically significant moments for the UK. However, they mark only the beginning of the Brexit process. Much still remains unknown about that process. Here are three outstanding issues.

Parliament's future role in the Brexit process

The Government has already announced that it will publish a formal policy paper (known as a "White Paper") setting out its negotiating strategy. There are no rules about what a White Paper must contain, nor any requirement that Parliament must debate or vote on it. It is not yet known whether the White Paper will be published before the Bill is through Parliament, although certain MPs have already called for a debate on the Government's strategy before they will vote in favour of the Bill.

The Government also intends to introduce a Great Repeal Bill into Parliament to repeal the 1972 Act and to prepare the UK's domestic law for Brexit. The Great Repeal Bill, expected in May 2017, is distinct from the current Bill and is highly unlikely to be as short, as it will address in detail the mechanism by which the Government intends to transpose existing EU law into UK law, "wherever practical". You can read our detailed analysis of the Great Repeal Bill here.

The Prime Minister confirmed on 17 January 2017 that the Government would put the final withdrawal agreement to Parliament, although it is not yet clear what the implications of Parliament voting against any proposed deal would be (as to which, see further below). In addition, beyond a vote at the end of the process, the Government is yet to commit to proposals in relation to the involvement of Parliament in the negotiations, other than to say that it will be "at least as well informed as the European Parliament as negotiations progress". We can expect Parliament's involvement to be a central point of contention when the Bill is debated later this week.

The role of the devolved administrations

The Supreme Court in Miller held that the Government is not under a legal obligation to seek consent from the Scottish, Welsh and Northern Irish devolved legislatures before triggering Article 50. The Court also stated that the Sewel Convention, a political convention whereby the UK Parliament will not normally legislate on devolved matters or the scope of devolved powers except with the consent of the devolved legislatures, was not legally enforceable.

However, while the Court said it would not "police" the operation of the convention, it did stress its constitutional importance, particularly in facilitating the harmonious relationship between the UK Parliament and the devolved legislatures. Is it possible that the convention should still be adhered to on political and/or constitutional grounds?

The Bill does not make provision for any devolution considerations. Scotland's First Minister, Nicola Sturgeon, has said that the Scottish Government will table a legislative consent motion in the Scottish Parliament regardless, while also warning that "time is running out" for the Government to "heed the voice of Scotland".

The Government has said that it wants the devolved administrations to be fully engaged in the Brexit process, but in relation to the triggering of Article 50 the Government's actions may speak louder than its words. In contrast, the Secretary of State for Scotland, David Mundell, has already indicated on behalf of the Government that consent will be sought from the devolved legislatures for the Great Repeal Bill.

Is Article 50 irrevocable?

As noted in our previous blog, the Supreme left open the question of whether Article 50 can be unilaterally revoked by the UK, once triggered, although it proceeded on the basis that it was irrevocable, without deciding the issue. Whether Article 50 is irrevocable or not could have significant implications for the UK's negotiating position, and for the importance of Parliament's vote at the end of the negotiation process.

The question is ultimately one of EU law and therefore would fall to be determined by the Court of Justice of the EU ("CJEU"). A case has been filed in the Irish High Court seeking a reference to the CJEU on this issue. If the Irish court makes the reference, it is possible that the CJEU could decide the issue before the end of the negotiation period.