This anti-theft device includes a stator (12), a rotor (14) mounted to rotate in the stator (12) between a first extreme angular position known as the “off” position and at least one second angular position, and a member (22) for interrupting the return travel of the rotor (14) from the second position to the “off” position in a position known as the “non-return” position interpolated angularly between the second position and “off” position, the interrupting member (22) being electrically deactivatable. The anti-theft device further includes a mechanical member (32) for deactivating the interrupting member (22).