This paper has a double purpose. On the one hand, it offers a new history, based on recently discovered primary sources, of the driving forces behind the so-called ‘constitutionalisation’ of European law taking place in 1963-64. On the other hand, it uses the lessons of this new history to reflect on how a general history of European law should be written and in particular how to avoid the pitfalls that characterises mainstream research on European law.

In the first part it is argued that the ‘constitutionalisation’ of European law was promoted by a broad coalition beyond the Court of Justice constituted by the Commission’s legal service, transnationally organised pro-European jurists and the European Parliament. When the Court of Justice in the two key judgments, Van Gend en Loos (1963) and Costa V. ENEL (1964), took the decisive steps to transform European law into a semi-federal legal order with direct effect and supremacy vis-à-vis national law, this coalition legitimised what had happened and contributed crucially to what would amount to a rather slow acceptance of the new ‘constitutional’ doctrines by national governments and courts. A key feature of these processes was the extent to which the emerging academic field of European law was deeply involved in legitimating the jurisprudence of the Court of Justice in the 1960s.

In the second part of the article, the starting point is to place mainstream legal and political science studies of European law in a historical perspective in order to explore to what extent academics continued to legitimise the Court of Justice in the 1970s, 1980s and 1990s. The conclusion is that mainstream research in the period defined the research object through the use of concepts and a historical understanding originally used to legitimise the ‘constitutionalisation’ of European law in the 1960s. This is in particular the case with the ‘integration-through-law’ paradigm that permeates most of the writing on European law even today.

Concluding, it is argued that a general history of European law should avoid the adoption of mainstream conceptualisations of the development of European law. To historians, mainstream legal and political science scholarship rather seems to be part of the research object.