In the European Union, food safety policies combine public regulations with private standards, in accordance with co-regulation principles. GLOBALGAP was initiated in 1997 by European retailers who developed a shared certification scheme inducing producers to comply with requirements on food safety, sustainable production methods, occupational health and animal welfare. The rise of standards in the governance of agri-food chains has been the subject of extensive debate among social scientists, based mainly on the issue of legal pluralism. Public regulations and voluntary standards are commonly presented as simultaneously competing with and reinforcing legal systems. The aim of this article is to discuss this assumption. First, we analyse GLOBALGAP as a repository, demonstrating that it is composed of heterogeneous types of prescription, such as good practice, proof recording and the rule of law, and that it covers many different issues (quality, environment, producer health, animal welfare, etc.). Second, we examine the issue of the rule of law within a voluntary standard and show that GLOBALGAP operates as a centre of calculation, bringing together separate existing elements of the law. As a consequence, the standard provides a material, organizational and cognitive support for a managerial rationalization of farms by actors such as consultants or producers organizations.