There is a brief provision in the United States Code at 28 U.S.C. Sec 1651, commonly called the All Writs Act, which simply states:
"(a) The Supreme Court and all courts established by Act of Congress may issue all writs necessary or appropriate in aid of their respective jurisdictions and agreeable to the usages and principles of law.
(b) An alternative writ or rule nisi may be issued by a justice or judge of a court which has jurisdiction."
A "writ" is a court order. A "rule nisi" is essentially a court order that is in some manner conditioned on an event. While this provision has a long history, the present language of the Act dates from 1948 and 1949 amendments. Essentially it is a blanket provision allowing court orders to enforce judicial actions.
Assistant United States Attorneys sought and received from Sheri Pym, United States Magistrate Judge for the U.S. District Court for the Central District of California, on February 16 an "Order Compelling Apple, Inc. to Assist Agents in Search." The Magistrate Judge based her authority to act on the All Writs Act. The order specifically identifies the cell phone in question and further orders Apple to provide specified types of technical assistance "to assist law enforcement agents in obtaining access to the data on the SUBJECT DEVICE." Apple is granted five days to appeal if it believes "that compliance with this order would be unreasonably burdensome."
While hundreds of court decisions have addressed the All Writs Act, only a very few U.S. Supreme Court decisions specifically mention this legislative provision. One may readily suppose that the Apple order might ultimately be heard by the U.S. Supreme Court.
A 1977 divided U.S. Supreme Court decision required New York Telephone Company to provide technical assistance to the government in installing pen registers (recording numbers called) on telephones (U.S. v. New York Telephone Company). That decision described the application of the All Writs Act as flexible and determined that requiring the assistance by the telephone company was not unreasonably burdensome since the company was already engaged in this activity for its internal purposes. Furthermore, the required assistance required minimal effort and would not be disruptive to the company's operations. The only privacy mention in that opinion was in passing reference to Congressional legislation. Of course, this decision also predates Justice Scalia's tenure on the Court.
Consequently, a very quick takeaway is that there is Supreme Court precedent for requiring a company to provide technical assistance related to telephones. However, the Apple order requires the company to provide more than minimal assistance and penetrates much deeper into the device. Privacy considerations abound.
My quickly formed legal intuition is that Apple may well win this case on several legal grounds including the amount of compelled assistance and privacy concerns. Of course, we will know the result in due course.
This comment provides a very brief and incomplete overview of a complex topic and is not intended to provide legal advice. Always consult an experienced attorney in specific situations.