Social norms facilitate coordination and cooperation among individuals, thus enable smoother functioning of social groups such as the highly distributed and diverse open source software development (OSSD) communities. In these communities, norms are mostly implicit and hidden in huge records of human-interaction information such as emails, discussions threads, bug reports, commit messages and even source code. This paper aims to introduce a new line of research on extracting social norms from the rich data available in software repositories. Initial results include a study of coding convention violations in JEdit, Argo UML and Glassfish projects. It also presents a new life-cycle model for norms in OSSD communities and demonstrates how a number of norms extracted from the Python development community follow this life-cycle model.