This article shows how cannabidiol regulation in Brazil enabled the development of lay expertise with influence in public institutions and policies. Cannabidiol is a compound identified in cannabis, with anticonvulsant potential. The text points out similarities of this experience with that of Aids activists in the 1990’s based on Steven Epstein’s analysis. Credibility, mobilization, mastery over the language of science and autonomy are among the factors that produce this distinguished layman. This work inquires, however, if this layman is representative of others and if he contributes to a more democratic science.