Cross-posted at Just Security.
The Ninth Circuit’s decision in United States v. Mohamud continues a trend of disappointing decisions by lower courts on the constitutionality of FISA Section 702 surveillance. There are many bones to pick with these decisions (see Jennifer Daskal’s earlier analysis here), but the most glaring flaw is the fundamental misunderstanding and misapplication of the “incidental overhear” doctrine. The courts are attempting to turn this doctrine into an exception to the warrant requirement, thus creating a hole in the Fourth Amendment that the Supreme Court has never sanctioned.
In brief, the panel’s reasoning was as follows: The targets of Section 702 surveillance, by law, are reasonably believed to be foreigners overseas, and are therefore not protected by the Fourth Amendment. Accordingly, no warrant is needed to collect their communications. In the domestic criminal context, a warrant need not specify the names of everyone who is in communication with the target in order to authorize acquisition those communications – a principle established in the 1970s in the so-called “incidental overhear” cases. The panel read these cases as holding that valid authority to conduct surveillance of a target carries with it the authority to acquire the communications of those in contact with him.
To understand where the panel went wrong, we need to start with certain undisputed cardinal Fourth Amendment principles. If Americans have a Fourth Amendment interest in their communications with foreigners, then a search or seizure those communications must be “reasonable.” And the Supreme Court has been quite clear that a warrantless search is “per se unreasonable” unless it falls within one of “a few specifically established and well delineated exceptions.” These exceptions are “jealously and carefully drawn,” with the Court having recognized fewer than ten of them.
The cases that established the “incidental overhear” principle did not purport to overrule these central tenets of Fourth Amendment jurisprudence, which have been restated by the Court many times since. Accordingly, the “incidental overhear” principle could justify dispensing with a warrant only if (1) a person has no Fourth Amendment interest (i.e., no reasonable expectation of privacy) in his or her communications with a surveillance target, or (2) the principle is itself an exception to the warrant requirement.
The first potential justification can quickly be ruled out. Nothing in the “incidental overhear” cases could be read to imply that Americans have no expectation of privacy in their communications with people who happen to be criminal suspects or otherwise subject to surveillance. The Ninth Circuit did not propose such a reading; it assumed that Mohamud had a Fourth Amendment interest in his communications, even though it found that his privacy interest was diminished by virtue of having transmitted his communications through third party carriers.
Accordingly, the “incidental overhear” cases would justify dispensing with a warrant only if they established an exception to the warrant requirement. This theory should immediately be suspect because the decisions in those cases did not use the word “exception,” let alone discuss the fact that one was being created. It is difficult to imagine that the Supreme Court would have added to the handful of “jealously and carefully drawn” exceptions to the warrant requirement without even saying so. Indeed, there was no need to find an exception, because the government had obtained a warrant in these cases (as discussed below).
Nonetheless, the Ninth Circuit, joining the FISA Court and two district courts that recently have addressed Section 702 surveillance, essentially treats these cases as having indirectly established an exception to the warrant requirement. The panel frames the “guiding principle” of the cases as follows: “[W]hen surveillance is lawful in the first place . . . the incidental interception of non-targeted  persons’ communications with the targeted persons is also lawful.” It follows from this principle that there is an exception to the warrant requirement for those in contact with people who may lawfully be targeted without a warrant.
But this is not, in fact, the principle that the “incidental overhear” cases established. In both United States v. Kahn and United States v. Donovan – the two foundational Supreme Court cases on this issue – the government had shown probable cause that a crime was taking place, and had obtained warrants allowing them to tap phones belonging to individuals suspected of involvement, in order to obtain the communications of those individuals and “others as yet unknown.” The defendants (who were among the “others as yet unknown”) argued that the lack of specificity regarding the targets of surveillance transformed the court’s order into a “general warrant,” thus violating the Fourth Amendment’s requirement of particularity.
The Court, however, observed that the Fourth Amendment’s particularity requirement extends only to the place to be searched and the persons or things to be seized. “In the wiretap context, those requirements are satisfied by identification of the telephone line to be tapped and the particular conversations to be seized.” The warrant also must require the government to “minimize the interception of any innocent conversations” – i.e., those not specified as being subject to seizure; it cannot leave the government “free to seize at will every conversation” taking place on the designated phone line. A warrant that contains these elements satisfies the warrant’s particularity requirement; it need not also identify “the persons from whom things will be seized.” The Court thus upheld the surveillance in these cases, not because no warrant was required for the persons “as yet unknown,” but because there was a valid, sufficiently particularized warrant that authorized collection of their communications.
In short, the central constitutional holding of the “incidental overhear” cases is that a warrant need not identify every person whose communications will be acquired in order to comply with the Fourth Amendment’s particularity requirement. Whatever merits might attach to the principle that those in contact with a surveillance target are not entitled to any legal process beyond what the target must receive, that is manifestly not the principle these cases espoused. (Indeed, if that were the applicable principle here, it is unclear why the Ninth Circuit proceeded to analyze whether the interception of Mohamud’s communications was “reasonable,” since he was in communication with a target for whom no “reasonableness” analysis was necessary.)
This error goes beyond an attempt to apply a rule to a set of facts where it is inapplicable. The panel fundamentally misunderstands the rule itself, and reads into the “incidental overhear” cases a principle that they do not support. In so doing, the Ninth Circuit joins other lower courts that are following the FISA Court down a major constitutional detour, and threatening the privacy rights of millions of Americans in the process.