Contrary to common opinion, the “pacifist principle” enshrined in Article 11 of the Constitution is not a fundamental reference for objectors and movements that support its recognition. That “repudiation” of war is in fact inscribed in an area of legitimisation of war itself, however limited to the defence of the homeland. The non-violent movements that advocate conscientious objection go further: these include the total renunciation of war as an ethical instance, starting with its preparation, the impracticability of defensive warfare in the atomic age, or a frontal opposition to the institution of the army, seen as an instrument of power of the ruling class. However, before I delve into the pacifist principles that animate conscientious objection, which have changed over the years, I intend to dwell on the notions on which Article 11 of the Constitution is based, as is evident from the acts of the Constituent Assembly. That debate, which took place between December 1946 and March 1947, helps us to understand the nature of a legal pacifism that affirms the repudiation of war as an instrument of offence or means of resolving international disputes, turning to the possibilities opened up by a new international law and the birth of the United Nations Organisation.