In his memoir, Althusser does not run to the law following his murder of Helene. He does not run into the street looking for a policeman. Rather, he runs to the 'sick bay' area of his apartment building (I think part of the Ecole, but I may be wrong) and hails Dr. Etienne, grabbing him and telling him that he, Althusser, had murdered Helene. In fact, Althusser notes that it was standard practice for someone suffering 'psychological disturbance' to be taken first to the police station. Yet, he was taken first to Sainte Anne's hospital.
How is, then, that law is absent at precisely that spot where Butler asserts its presence? In fact, she hears the voice of law ushering from a place where law is completely absent, displaced by the medical-psychiatric apparatus.