The core of the task facing the Supreme Court in Cherry/Miller was to interpret and apply constitutional and legal principles. One of the striking things about the judgment is the forthrightness with which the justices set out their collective view about how the constitution should be interpreted. The Supreme Court’s judgment stated in clear terms that the separation of powers is fundamental to how the UK constitution operates (a point I explore further elsewhere). What I want to address here is whether it is right to say that the Court’s approach to constitutional interpretation was political and therefore problematic.

My basic starting point is that all exercises of constitutional interpretation, when undertaken by a constitutional actor, are political. It is obvious but worth stressing that within the judiciary, and as well as within government and Parliament, there are conflicting views about the meaning of constitutional principles and how they should apply in particular contexts. I do not think it is possible to regard such questions as being purely ‘legal’ and to be entirely divorced from political judgments. For example, whether or not you believe that parliamentary sovereignty is relevant to the question of prorogation is likely to be informed by broader constitutional perspectives which are inherently political. One should not single out the Supreme Court’s judgment as unusually political. The High Court’s judgment in Miller (No 2), and the way it approached the key questions of constitutional interpretation, was just as political as the Supreme Court’s judgment insofar as it relied on, and set out, a clear view on how the constitution should operate. In a sense, this reveals that the problem with characterising a judgment as ‘political’ is that there is no agreed definition of what the term means in this context.

Part of the problem is that the high-profile nature of the case and the circumstances of Brexit encourage an overly hasty conclusion that the Supreme Court’s judgment is abnormally political. However, there is also a more considered view that by deciding to articulate a legal test to apply to prorogation, the Court made an inherently political decision to intervene. In response, I would argue that to characterise this form of politicisation as problematic is wrong. The independence of the judiciary does not mean that judges cannot take political positions on the meaning of the constitution. On the contrary, this is part of the core constitutional role of the courts.

A useful analogy can be drawn with the role of the Speaker of the House of Commons. The current Speaker has been repeatedly criticised for an ‘activist’ approach to interpreting procedural rules. However, the Speaker has defended himself on the basis that he must interpret the rules in line with his view of their underlying purpose to ensure that Parliament’s pre-eminent constitutional role is upheld. So the current Speaker’s approach is not unduly political: constitutional interpretation is inherently connected to underlying political perspectives on the constitutional functions of the relevant institutional actors.

To conclude, when the constitution is under strain from all sides, it is normal that Parliament and the judiciary are asked to make decisions on questions of constitutional interpretation which are inherently political. It would be wrong, in my view, to characterise the Supreme Court’s judgment as improper simply because it is based on a particular view of the role of the courts and Parliament in the UK’s constitutional order.

Jack Simson Caird is Senior Research Fellow in Parliaments and the Rule of Law at the Bingham Centre for the Rule of Law