On Thursday, the legislation for Article 50 notification gets royal assent. The Queen does not do this personally — no monarch has done so since 1854. This is unlike bills signed by, say, US presidents. But royal assent is what makes a bill an Act of Parliament. The power of the prime minister to make the notification is now part of the law of the land.
There is a somewhat academic question of what at law constitutes the decision of the UK to leave the EU as required by Article 50 before such notification is sent. I deal with that geeky constitutional law question here.
But the significance of the new act of parliament is that it is now, once again, in the hands of the prime minister. In legal(istic) terms, we have reverted to the position Theresa May thought she was in before the High Court decision in the Miller litigation. She can now make the notification at a time of her own choosing. Read more