Legal Case Summary
Macarthys Ltd v Smith [1979] (Case 129/79)
Established that domestic law ought be interpreted in light of EC law, with EC law prevailing in the event of conflict.
Facts
The claimant, Ms Smith, was a factory employee of the defendants, Macarthys, for which she received a salary of £50 per week. She complained that the man who had previously held the same job in the company had received £60 per week, and thus that the defendants were in breach of both the British Equal Pay Act 1970, as well as Article 119 of the EC Treaty. The defendants contended that the domestic statute was inapplicable as it did not provide for comparisons of salary with former employees to which Ms Smith responded that this did not negate the applicability of EC law in which comparisons were permitted. Further, Ms Smith submitted that where UK and EC legislation was incompatible on the matter, EC law would prevail.
Issues
Whether UK or EC law ought have supremacy in the event of conflict.
Decision/Outcome
The Court of Appeal found against Ms Smith, on the grounds that EC treaties were not a factor in the interpretation of domestic law. Notably Lord Denning dissented, on the grounds that the Court ought presume that Parliament ‘intends to fulfil its obligations under the Treaty’ and had not given any indication that it thought earlier British law ought prevail over EC laws on the matter.
The case was then referred to the European Court of Justice where it was held that Ms Smith was entitled to compare her salary with that of a former employee, giving approval to the statement provided by Lord Denning in dissent. Subsequently, the Court of Appeal then found for Ms Smith as per the European court’s order.
Updated 20 March 2026
This article accurately summarises the key legal principles established in Macarthys Ltd v Smith [1979] ICR 785 (CA) and Case 129/79 (ECJ). The case remains a significant authority in UK constitutional and EU law history, particularly regarding the primacy of EC law over inconsistent domestic legislation and the interpretive approach endorsed by Lord Denning.
Readers should note, however, that the constitutional and legal context described in the article no longer reflects the current position in UK law. Following the UK’s withdrawal from the European Union, the European Union (Withdrawal) Act 2018 (as amended by the European Union (Withdrawal Agreement) Act 2020) ended the supremacy of EU law in the United Kingdom. Retained EU law was brought into domestic law as a form of domestic statute, and the European Union (Retained EU Law) Act 2023 has since made further significant changes to the status and treatment of that retained EU law. The principle of EU law supremacy that this case illustrates is therefore now of historical importance rather than ongoing practical application in domestic UK courts. The Equal Pay Act 1970 itself was repealed and consolidated into the Equality Act 2010, which remains in force. The case retains considerable academic and historical importance for understanding the development of EU law primacy doctrine and its relationship with UK parliamentary sovereignty during the period of EU membership.
