With the massive repression unleashed by the military coup, the definition of the boundaries between law and extralegal force immediately emerged as potentially the most explosive point of contact between the judiciary and the military regime. As in any legal system conforming to the rule of law, Chilean constitutional and statutory law stipulated that all arrests had to comply with strict guarantees protecting individual freedoms, incarceration could only follow conviction by trial, and, even under constitutional states of emergency, such as the state of siege, due process remained in force and the scope of emergency powers was delimited. In the days following the coup, before the onslaught of repressive military power, these norms faded from the horizon. Mass detentions, summary executions, bodies in the Mapocho River, and the first military tribunals were clear signals that the precise argument of lawyers had given way to time of war, as the military itself characterized the period for legal purposes.

Nevertheless, despite this abrupt displacement, under the constitution the judiciary held the authority, if not the power, to see that these transgressions were corrected. The judiciary's relevant authority in this new context was twofold. First, on petition, the judiciary was empowered to uphold constitutional guarantees of due process and protect persons from arbitrary arrest. The instrument was the recurso de amparo, a writ similar to habeas corpus, which on appeal could proceed to the Supreme Court. Second, although the declaration of a state of siege gave military courts jurisdiction over most political offenses, the constitution authorized the Supreme Court to supervise all courts, which implied that the Court held the authority to review and correct the administration of military justice.