Proactive transparency in the form of electronic provision of documents is required by law in the EU. It has long been acknowledged in law and technology studies that digital technology can have legal consequences when implemented to perform a legal function. Consequently, the technological design of document registers has the ability to limit as well as enhance access to documents. When technology can have such regulatory powers, incorporating it into a legal function requires closer attention as to how or why it is so. This article will provide a close analysis of the European Commission’s main Register of Documents (RegDoc) to study the implications of technological design for access to documents. Transparency is approached through a procedural view, highlighting its mechanisms. The article uses a HCI based walkthrough method for the case-study artefact critique of the RegDoc. The main findings suggest that there are two specific affordances of the RegDoc that limit access, especially for users who do not have pre-existing knowledge of the documents they are searching for. These affordances are, first, the scope of the dataset and, second, searchability. Overall, designing technology for legally relevant functions should take into account the wider legal framework that the technology aims to cater for. Attention should be paid to the affordances that can make a legal difference in a technology created to perform a legally relevant task.