R v Secretary of State for Foreign Affairs, ex p Lord Rees-Mogg [1994] QB 552
Established the legality of the Government signing an international treaty which did not alter national laws, and thus did not impede upon Parliament’s sovereignty.
Facts
The claimant, Lord Rees-Mog, was a noted journalist and life peer of the House of Lords, who sought judicial review on the legality of the defendant’s signing of the Maastricht Treaty, which recognised Britain’s joining of the European Union. The claimant’s submission was that as Parliament was sovereign in Britain, it could not reduce or transfer certain powers (for instance regarding some social policies) without statutory authority, which Lord Rees-Mog did not believe had been satisfied as Parliament had not directly approved the Treaty’s signing.
Issues
Whether the signing of the Maastricht Treaty operated to illegally curtail the Crown’s prerogative.
Decision/Outcome
The Court declined to give judicial review, finding that the European Communities (Amendment) Act 1993 described a process for protocol ratification which Parliament had approved. Moreover, Lloyd LJ commented that ‘It is axiomatic that Parliament alone can change the law… treaty-making power is part of the Royal Prerogative’. Further, the content of the Treaty would not operate to alter the content of any domestic British laws, and thus the matter did not impact Parliament’s legislative sovereignty.
Further notable here is that the Court’s willingness to hear the case displays the adoption of a flexible and expansive understanding to lex loci in regards to judicial review, whereby a party who wishes to bring a claim ought be able to demonstrate sufficient standing of connection to the case.
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Updated 20 March 2026
This case summary remains broadly accurate as a description of the 1994 judgment. The core legal principles discussed — the Royal Prerogative in treaty-making, parliamentary sovereignty, and the role of the European Communities (Amendment) Act 1993 — are correctly stated.
Readers should be aware of one important contextual development: following the United Kingdom’s withdrawal from the European Union, the legal and constitutional landscape surrounding EU treaties and EU-derived law has changed substantially. The European Union (Withdrawal) Act 2018, the European Union (Withdrawal Agreement) Act 2020, and related legislation have fundamentally altered the UK’s relationship with EU law. While none of this affects the correctness of the decision as a matter of 1994 law, it means that much of the EU treaty framework the case concerned no longer applies to the UK in the same way. The case retains its relevance as an authority on the prerogative power to conclude treaties and its relationship with parliamentary sovereignty, but students should treat the EU-specific context as historical.
The article’s final paragraph concerning locus standi (standing) is broadly accurate in substance, though the Latin term used (lex loci) is incorrect — lex loci refers to the law of the place, not to standing. The relevant concept is locus standi. This is not merely a stylistic point; using the wrong legal term could cause genuine confusion for students.
