Legal Case Summary
Blackburn v Attorney General [1971] 2 All ER 1380
Affirmed Parliament’s right to sign the Maastricht Treaty and thus voluntarily give some of its powers to the EC, despite the principle of Parliamentary sovereignty.
Facts
The claimant, Blackburn, asserted that the decision by Parliament to allow Britain to join the Economic Community and sign the Maastricht Treaty was illegal as it diminished their own sovereignty, and violated the theoretical conception of the ‘Queen in Parliament’, whereby all power is vested in the Crown and subsequently in Parliament. Thus, Blackburn sought a judicial review.
Issue
Whether Parliament had the authority to enter Britain into the European Community and voluntarily relinquish some of their own powers.
Decision / Outcome
The Court of Appeal held that Britain’s decision to join the Economic Community did not amount to an illegal surrendering of Parliamentary sovereignty. Further, the very nature of Parliament’s supreme sovereignty meant that they could ‘enact, amend and repeal any legislation it pleases’, and as Parliament voluntarily elected to recognise EC law, this was not an intrusion on their sovereignty. Moreover, it was beyond the jurisdiction of the Courts to perform a judicial review on Parliament’s rightful exercise of its prerogative powers. Furthermore, as Parliament was unable to bind successive Parliaments, any delegation of powers to the EC was reversible. Notably, the decision was not unanimous with Lord Denning dissenting on the grounds that the Statute of Westminster 1931, which granted powers to British dominions, meant that Parliament was not empowered to place subsequent reductions on the powers given to the dominions by giving them to the European Community.
Updated 19 March 2026
This summary contains several legal inaccuracies that students should be aware of.
Most significantly, the article repeatedly refers to the Maastricht Treaty in connection with this 1971 case. This is factually wrong: the Maastricht Treaty was signed in 1992, more than twenty years after this decision. The 1971 case concerned Britain’s proposed accession to the European Economic Community under the Treaty of Rome, which was subsequently given domestic effect by the European Communities Act 1972. The Maastricht Treaty played no part in Blackburn v Attorney General and students should disregard any reference to it in this summary.
The summary’s description of Lord Denning’s dissent is also potentially misleading. Lord Denning did not dissent from the outcome; the court was unanimous in refusing the application. Lord Denning did, however, make the observation about the Statute of Westminster 1931 in the course of his judgment. Students should consult the original report for an accurate account of each judge’s reasoning.
On the substantive legal principles — parliamentary sovereignty, the irreversibility argument, and the court’s refusal to review the exercise of treaty-making prerogative powers — the summary broadly reflects the reasoning in the case as reported. However, students should note the significantly changed constitutional landscape: the United Kingdom left the European Union on 31 January 2020 following the European Union (Withdrawal) Act 2018 and the European Union (Withdrawal Agreement) Act 2020, and the European Communities Act 1972 was repealed. The case retains historical and doctrinal interest on parliamentary sovereignty and the limits of judicial review of prerogative powers, but its specific EU context is now of historical significance only.
