The Court of Justice of the European Union has historically rejected references to preparatory work in the interpretation of EU Treaties. However, the preparatory work for the EURATOM, Maastricht, and Constitutional Treaties have played a role in recent judgments. The ‘explanations’ to the Charter of Fundamental Rights are expressly approved in the current Treaties. We examine the emerging case law on preparatory work. Reference to the drafters’ intent does not necessarily support dynamic interpretation, and may potentially even ossify historical interpretations. Even if the consequence of their introduction is a conservative interpretation, their use raises questions of transparency and democracy, and complicates the already difficult task of interpreting the EU constitution.