For want of public regulations for organic agriculture in Morocco, stakeholders chose to develop their own label and a Participatory Guarantee System (PGS). In this paper, we present the Participatory Action Research that led to the emergence of a PGS for local markets. Theoretically, we consider this mode of governance - by delegating to the peer community the definition of what is the local norm, and the control of this one - as a type of knowledge commons. Based on an evaluation of the Participatory Action Research, we question to which extent it could lead to a common vision, influence the design, appropriation and improvement of rules for the PGS schemes and, lastly, contribute to the emergence of a commons. We applied the grammar of institutions to describe the outputs of the participatory process. Substantial results show that the different components of the knowledge commons are now available to the community and are fairly well appreciated by the participants. Operational results suggests that the PGS still faces challenges, especially when it comes to scaling-up. We finally propose a critical analysis of the participatory approach used to build this type of socio-economic innovation as a knowledge commons and discuss the conditions required for replicating a knowledge commons in and beyond the context of Morocco.