http://www.politico.eu/article/france-to-reinstate-border-controls-during-cop21/
Implementatation isn't clear yet, but this could be a hassle at CDG for Schengen arrivals and even Schengen to non-Schengen connections. Given that it will start in a week, and that CDG isn't organized any more for so many passport-controlled flights, I'd rather arrive early, and if possible schedule enough time for connections..