This paper is derived from the ambition to analyze inter-organizational collaboration in so-called bottom-up projects. These projects have the particularity to be conducted by extremely diverse groups of actors, and the theory of boundary object lends itself very well to their comprehension. However, it doesn't allow to consider the different levels of context that impact the projects. We propose to combine it with a regulation approach, in order to take into account the meso and macro articulations and constraints. We proceed by a comparative and multilevel case study of : 1/ a French cluster in the field of eco construction (PTCE), 2/ an emerging Natural Park in Mexico. Our findings overcome monocausal explanations and provide insights in the contradictions between the local institutional arrangements of the projects and the meso and macro institutional mechanisms.