We discuss the application of deontic logics to the modeling of variabilities in product family descriptions. Deontic logics make it possible to express concepts like permission and obligation. As a first result of this line of research, we show how a Modal Transition System, a model that has recently been proposed as an expressive way to deal with behavioural variability in product families, can be completely characterized with deontic logic formulae. We moreover show some exemplary properties that can consequently be proved for product families. These preliminary results pave the way to a wider application of deontic logics to specifiy and verify variability in product families.