Internal borders are a major but understudied site of crimmigration as most scholarship has focused on external borders (Van der Woude and Van Berlo, 2015). Internal borders were supposed to disappear under the principle of free movement within the European Union. But today we see EU member states policing the borders inside Schengen, checking identification, verifying passage, and regulating mobility in so-called 'gray zones'. This article investigates this type of policing within the EU, focusing on the case of the Netherlands. It argues that the policing of internal borders is highly dependent upon discretionary power, a significant factor in the crimmigration process that we do not know enough about. Following Hawkins (1992, 2003), Schneider (1992), and Bushway and Forst (2013) on discretion and discretionary decision-making, we examine the interaction between decisions by law-makers and policy-makers that create discretionary space for law enforcement officials on the ground, and the way in which these street-level bureaucrats perceive the discretionary space attributed to them. By zeroing in on the interaction between these two actors, we aim to find the discretionary decision that matters the most in terms of explaining the crimmigration practices, offering a more holistic and interdisciplinary approach to border control. We discuss the implications of this power and the consequences for the European Project as such.