This article delves into the history of the negotiations of the ‘Luxembourg protocol’ of 1971, which conferred jurisdiction upon the European Court of Justice (ECJ) for the interpretation of the 1968 Brussels convention. The protocol provided a preliminary ruling procedure that had undergone restrictive modiﬁcations in comparison with the European Economic Community (EEC) treaty’s original (Article 177). Some have, therefore, interpreted the outcome of the negotiations as a sign that the mechanism was being criticised in national administrations. This article will, for the ﬁrst time, bring to the surface archival evidence to explain why the protocol contained an altered version of Article 177 EEC. Furthermore, it will reveal that the governments’ experts’ intention to limit the procedure in the protocol caused serious concern inside the ECJ, of which some members consequently repeatedly urged national decision-makers to opt for formulas identical with Article 177 EEC.