To certify French competences of the foreign candidates, new students need either C1 or C2 level of language competece. These diplomas are delivered by the French National Education board to certify French competences of the foreign candidates. In other words, if you posesse already one of these diplomas, you are exempt from taking language tests for entrance into French universities. (info source link: http://goo.gl/7moL2N
Whether you need C1 or C2 is different for different universities and/or subjects. One of the Paris regional universities, the University of Cergy-Pontoise, states very clearly for their new students, the new students require:
• B2 level for the faculty of Sciences and Technology and the faculty of Languages,
• C1 level for the faculty of Economics, Management & Finance and for the Law School
• C2 level for the faculty of Humanities and Social Sciences.
(info source link: https://goo.gl/vvwXwT