The COLEX project (Coopetition and Legislation) aimed to produce unprecedented and original research on the (in)effectiveness of legislation promulgated in the name of the Spanish King in the Spanish Netherlands (currently Belgium, the Grand Duchy of Luxembourg, the Netherlands and Northern France) during the reign of the Archdukes Albert and Isabelle (1598-1621) and Philip IV of Spain (1621-1665). In order to study carefully the chosen theme, we will rely on the concept of coopetition. The chosen period should allow for a comparison of legislation enforcement since the reign of the Archdukes, starting with the death of King Philip II, after which the Netherlands was ceded to the archducal couple, until the death of King Philip IV. This period was a pivotal moment in the history of these territories. After the Revolt started by the Northern provinces in the 1560s against Philip II, the government of the Archdukes saw the introduction of temporary peace with the enemy Dutch Republic (Twelve Years’ Truce, 1609-1621). However, in the year 1621, conflict between them returned and they joined a European war that had already begun (Thirty Years’ War, 1618-1648). The Netherlands, part of the vast Spanish Monarchy since the end of the 15th century, are a prime area in which to try to understand the logic that governs the decisions in the field of law enforcement. If there is a representative of the monarch in Brussels - the governor-general - he must take into consideration the political culture of these principalities that are characterised by the involvement of subjects (towns, trades, merchants, etc.) in the decision-making process. Moreover, this involvement manifests itself in different ways (petitions, appeals, draft legal acts, etc.). The case of the Netherlands is not only interesting in its own right, but also from a comparative perspective with other territories of the Spanish Monarchy in the early modern era.