3.2.2.3 - Comparing the Judiciaries

Comparative Frame

Both the UK and USA have a supreme court. That similarity can mislead students. "Supreme Court" does not mean the same constitutional position in each system.

The strongest structural comparison is this: the UK Supreme Court is supreme in the court hierarchy, but Parliament remains legally sovereign. The US Supreme Court is supreme within a constitutional order where the Constitution is higher law. That structure gives the US Court a stronger ability to block elected branches.

The strongest rational comparison is this: UK ministers and Parliament can often respond to court judgments through new legislation or policy revision. US Presidents, senators, litigants and pressure groups have incentives to fight over Supreme Court appointments and litigation because one constitutional ruling can be difficult to reverse.

The strongest cultural comparison is this: UK legal culture tends to stress legality, parliamentary sovereignty and professional judicial appointment. US political culture gives constitutional text, rights claims, original meaning, living constitutionalism and Supreme Court appointments much greater public salience.

Power Bases

The relative power of the two courts comes from their constitutional bases.

The difference between UK and US judicial review is crucial.

UK judicial review process:
Public body or minister uses legal power
-> claimant argues the power was used unlawfully
-> court checks legality, fairness, reasonableness or rights compatibility
-> court may quash, declare or require reconsideration
-> Parliament can still legislate clearly if it chooses

US constitutional review process:
Federal, state or executive action is challenged in a legal case
-> courts decide whether the action conflicts with the Constitution
-> Supreme Court may give final constitutional interpretation
-> unconstitutional law or action cannot stand
-> reversal usually requires constitutional amendment or later Court reversal

Structurally, the US Court is more powerful because constitutional supremacy gives it a standard above ordinary law. The UK Court is powerful against ministers and public bodies, but not normally against Parliament itself.

Rationally, this changes behaviour. A UK government that loses in court may change guidance, remake a decision, or pass legislation. A US President or Congress facing an adverse constitutional ruling cannot simply pass the same law again and expect it to survive.

Culturally, this explains why US politics treats Supreme Court appointments as battles over constitutional direction, while UK politics usually treats senior judicial appointment as a professional legal process, even when judgments become politically controversial.

Active reading: In which country is a court judgment against ordinary legislation harder for elected politicians to reverse, and why?

Political Impact

Courts are not elected policy-makers, but both supreme courts can affect government and politics. The key comparative question is not "Do courts matter?" Both do. The better question is "What kind of impact can each court have, and how far can political branches respond?"

The UK Supreme Court's impact is often strongest where government power meets legality. It can decide whether ministers have legal authority, whether public bodies acted fairly, whether rights duties were respected, and whether executive action exceeded constitutional limits. This matters in politics because legal defeat can halt a policy, force a new process, embarrass ministers or require Parliament to legislate openly.

But UK impact is limited by parliamentary sovereignty. A UKSC judgment does not usually remove an Act of Parliament from the statute book. Human Rights Act section 4 declarations of incompatibility identify a rights conflict, but the law remains valid and Parliament decides whether to amend it. The Safety of Rwanda (Asylum and Immigration) Act 2024 after AAA shows the pattern: the Court's judgment mattered, but elected branches retained a route to respond.