This is what the Bill says:

You’ll see that the operative clause says:

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.

And here’s what the relevant bits of Article 50 says:

You’ll see that the UK has to make a decision to withdraw from the EU (clause 1). And then notify the Council of that decision (clause 2).

Now the Bill authorises the Prime Minister to notify the decision. But it says nothing about who gets to make the decision.

It is true that the judgment of the majority in the Supreme Court focuses on notifying the decision: see, for example, paragraph 59 which provides:

And paragraph 101:

On the other hand, when the majority  turns to considers the effects of the Referendum, it is quite clear that the Referendum does not constitute the decision to leave:

And that’s because the force of the Referendum lies in the way it influences Parliament:

In so deciding, the Supreme Court rejected the contention advanced by the Attorney General in the High Court that the decision had been made (see pages 59-61 here):

The first point is that the former Prime Minister, David Cameron, in a speech on 23 January 2013, in which he announced his intention that should the Conservative party win an overall majority in the forthcoming general election, to hold what was described as a referendum.

Secondly, a majority Conservative government having been elected in the general election on 7 May 2015, the European Union Referendum Bill was introduced in Parliament on 28 May and became an act on 17 December that year. It provided for a referendum asking the question: should the UK remain a member of the European Union or leave the European Union. We will submit that it was clear during the passing of that legislation that the government intended to act in accordance with the outcome of the referendum. (Pause)

The third point I was going to make was that the referendum itself took place on 23 June 2016, with a clear majority of those voting in favour of leaving the European Union.

Fourthly, the then Prime Minister made it clear on 24 June that the will of the British people expressed in the referendum result would be respected and acted upon.

Fifth, on the resignation of David Cameron as Prime Minister, the current Prime Minister announced her candidacy, saying she would also act on the result of the referendum.

Sixth, on becoming Prime Minister, Theresa May has made it clear repeatedly that the government will deliver the departure of the United Kingdom from the European Union and statements of other ministers have confirmed the same. So my Lords, it is the defendant’s clear contention that by the steps I have set out, a decision has been taken by the government to leave the European Union in accordance with the provisions of Article 50(1) of the treaty on European Union. And in accordance with Article 50(2) of the treaty, the next step to be taken is the notification of that decision to the European Council.

So if the Referendum is not the decision to leave, and the decision has to be taken by Parliament, where is the decision?

Perhaps the Government thinks that Parliament, should it authorise the Government to notify, is implicitly making a decision? Perhaps, should the Bill be enacted in this form, a court would agree that it has been made?

But, at a momentous moment like this, it’s an awfully odd way to legislate. It might be an idea for the Government to amend its own Bill.