Very interesting, what you quoted from Twitter, Esk.
If I may quote a certain part of it:
"...The ECA 1972 cannot be regarded as silent on the question of what happens to EU rights in domestic law if the Crown seeks to take action on the international plane to undo them. Either the Act reserves power to do that, including by giving notice under Article 50, or it does not. In our view, it clearly does not..."
Now the above may be legal dynamite. Legal dynamite for the Judges, I might add.
For the following reasons (and I'm not being flippant when I put this together):
1. Direct reference is made to undoing rights if the Crown seeks to take action on the matter (i.e. overturn what has previously been enacted by Parliament via an Act of Parliament).
2. Three thing happen/can happen to an Act of Parliament: 1. it is enacted when finally passed; 2. it is changed by subsequent amending Regulations; and 3. it is repealed.
3. Now I come to the crux of the matter. This sentence: "Either the Act reserves power to do that, including by giving notice under Article 50, or it does not." And the crux is this: if Article 50 is enshrined in a present, ongoing, Act of Parliament, then it is for the Government of the day to determine if that legal enshrinement should be acted upon. While that Act is current, it is for the Government to decide whether to act on it, or not (NOT Judges).
4. And this is where I see the legal problem. What has been said, on the Judges's say-so, is that the Government does not have the legal clout or authority to go along the road of implementing Article 50, which Article is current and legal. In saying "In our view, it clearly does not." they are saying that Article 50 cannot be invoked to undo EU rights in domestic law by taking action on the international plane (to withdraw from the EU, in other words).
5. By what I have explained in '4' above, Judges are interfering directly with the operations of the State. Nothing less. They may seek to claim that they are simply making a legal ruling on the interpretation of the wording of an Act of Parliament. However, it is one thing to rule on the wording of an Act, it is another thing altogether to interfere with the intent.
6. I haven't read the full decision of the Judges (but am interested in doing so), but I believe they would have to show that a part or parts of the Act they have examined are considered to be ultra vires for their decision to carry legal weight. It is only by saying that what is presently contained in the relevant legislation has gone beyond what is legally permissible, that their judgement today will carry the day in a subsequent appeal to a higher court.
It's gonna be a very interesting next few months, either way.
Apologies, also, for the long post.