In a theoretical and a methodological perspectives, my paper analyses the constitutional evolution of party pluralism, basing on the model of "militant democracy," (Loewenstein,1937), characterized paradoxically by legal restrictions on the access for the parties to elections grounded axiologically. My case study, Algeria, is not this liberal democracy about which Loewenstein was building his conceptualisation. But it is relevant to show how « rules matters » in a non democratic regime, through the Constitution wich define in particular « what acceptable » and « unacceptable » (Ginsburg, Simpser, 2014) in a specific point : the party pluralism. Algeria had the first democratic experience,from 1989, before the "Arab Spring". Characterized by widespread liberty of expression, it came to an abrupt halt. The legislative elections carried by the FIS Islamic Salvation Front on 1991 were cancelled by the government and the military leadership. This was followed by a decade of civil war and terrorism. If the academic literature, one element neglected : the transformation of the Constitutional and legal definition of "actors allowed to participate in the electoral competition" (Aït-Aoudia 2015). The Constitutions of 1995 and 2016 change the frame of the party pluralism in a restriction way comparing to 1989. The new legal conditions for recognition of parties, drawing support from the dramatic failure of the democratic experience, constitute a new definition of legal pluralism.