The decision by the government of Tony Blair to puff up the judicial committee of the House of Lords into the new Supreme Court a few years ago might well have been a mistake.
Views vary as to whether it should, the other day, have ventured onto new political ground. What is not in serious dispute is that it has ventured onto that new political ground. The judgment of the court claims that there is nothing wrong with that. It includes this:
- Secondly, although the courts cannot decide political questions, the fact that a legal dispute concerns the conduct of politicians, or arises from a matter of political controversy, has never been sufficient reason for the courts to refuse to consider it. As the Divisional Court observed in para 47 of its judgment, almost all important decisions made by the executive have a political hue to them. Nevertheless, the courts have exercised a supervisory jurisdiction over the decisions of the executive for centuries. Many if not most of the constitutional cases in our legal history have been concerned with politics in that sense.
This last sentence may be doubted. Certainly, it is contrary to the views of the Lord Chief Justice and the other members of the Divisional Court as expressed in Miller, R (On the Application Of) v The Prime Minister  EWHC 2381:
42 The criteria adopted by the courts for identifying non-justiciable exercises of prerogative power are whether they involve matters of “high policy” or are “political”. In this way the courts, whose function it is, have marked out the separation of powers between the judicial and the executive branches of government, a fundamental feature of our unwritten constitution. In the present case the Prime Minister contends that the advice to Her Majesty to prorogue Parliament, which was given effect in the Order in Council of 28 August 2019, was political.
43 The refusal of the courts to review political questions is well established. In A v Secretary of State for the Home Department  1 AC 68, Lord Bingham said (at ) in relation to the application of Article 15 ECHR and whether there was a public emergency threatening the life of the nation:
“The more purely political (in a broad or narrow sense) a question is, the more appropriate it will be for political resolution and the less likely it is to be an appropriate matter for judicial decision. The smaller, therefore, will be the potential role of the court. It is the function of political and not judicial bodies to resolve political questions.”
64 The constitutional arrangements of the United Kingdom have evolved to achieve a balance between the three branches of the state; and the relationship between the Executive and Parliament is governed in part by statute and in part by convention. Standing Orders of both Houses elaborate the procedural relationship between the Executive and Parliament. This is territory into which the courts should be slow indeed to intrude by recognising an expanded concept of Parliamentary Sovereignty.
Whatever your view about these things, it is clear that the genie is out of the bottle. The cat is out of the bag. The tiger has tasted the flesh of the villagers. However noble the idea that judges should be entirely neutral and apolitical, the reality is that the political leaning of judges who venture onto political ground is bound to come under scrutiny. There are already analyses of the political leanings of the Supreme Court, and unsurprisingly, people are concluding that the Supreme Court has a strong political leaning against Brexit.
The Supreme Court of the United States has been involving itself in political matters for a long time, and there are in place in the United States constitutional arrangements designed (broadly) to obtain a political balance in that Supreme Court.
Now that the Supreme Court of the United Kingdom has followed suit, so also the appointment system now has to be changed to obtain a political balance in that court also. We might not need a comprehensive written constitution, but we do need some constitutional principles brought into law now to reshape which judges sit in the Supreme Court. At the moment, appointment is on the advice of the Selection Commission, which consults with senior judges. That system is plainly failed to achieve political balance (or at any rate, to demonstrate any political balance) and so the right course (which will probably have to wait until we get a new House of Commons following a general election) will be to remove all of the present judges and to replace them as necessary by a new system. A sensible balance would be for the court to consist of judges who are broadly, but not entirely, in sympathy with the policies of the government of the day. That way, the Supreme Court would be able to declare on the law, so as to rule against any conduct which is truly unlawful, without setting itself up in competition with the policies of the government of the day.
 I am not alone in holding the view that it should not; my observations are at https://phenell.wordpress.com/2019/09/25/before-the-cock-crow-thou-shalt-deny-me-thrice/#more-5389.