This is really important. Clearly the Courts have every right to rule on the issues that are brought before them, and we must abide by their decision. That is not in doubt. The Courts created new law and set new precedent in their judgement. Again they have every right to do that where gaps exist in the law, however this particular decision is bound to be controversial and could have a huge impact for generations to come.
Worth noting that the law the Prime Minister has supposed to have broken didn't actually exist when he made the decision to prorogue. It only appeared as a result of the decision by the Supreme Court yesterday.
There are long term consequences to the decision to allow courts to rule on the Royal Prerogative, and on issues like prorogation. In the future we could well see that any individual is able to prevent things like elections or Queen's Speeches, or possibly any other decision made by Government, through the courts.
This isn't just about Brexit and the here and now, it will limit the powers of all Governments in the future. In my view that also takes power away from elected politicians (and therefore away from voters at the ballot box), and hands that power to those who can afford fancy lawyers. I do not believe that is a good thing.
The Attorney General set this out very clearly.