The South Florida Sun-Sentinel provides us with one more data point showing the growing frequency with which police are using cell phones as tracking devices—a practice whose surprising prevalence the ACLU shone light on in April. In fiscal year 2011-2012, the first year Florida kept tabs on cell location tracking, state authorities made 171 location tracking requests—and apparently hope to expand the program.

The article alludes to a couple of specific cases in which location tracking was employed—to find a murder suspect and a girl who was thought to have been kidnapped—both of which are perfectly legitimate uses of the technology in principle. In general, if there’s enough evidence to issue an arrest warrant, the same evidence should support a warrant for tracking authority when the suspect’s location isn’t immediately known. In cases where police have a good faith belief that there’s a serious emergency—such as a suspected kidnapping—it’s even reasonable to allow police to seek location information without a court order, as is standard practice with most other kinds of electronic records requests. But the Sun-Sentinel report is also unsettlingly vague about the precise legal standard followed in non-emergency cases. According to a law enforcement official quoted in the story, the Florida Department of Law Enforcement’s Electronic Surveillance “always seeks judicial approval to trail someone with GPS,” while the written policy only “instructs agents to show probable cause for criminal activity to the department’s legal counsel to see if a court order is necessary,” implying that it sometimes is not necessary.

The term “court order,” however, is quite broad: the word that’s conspicuously absent from these definitions is “warrant”—an order meeting the Fourth Amendment’s standards. In the past, the Justice Department has argued that many kinds of location tracking may be conducted using other kinds of authority, such as so-called “pen register” and “2403(d)” orders. Unlike full-fledged search warrants, which require a showing of “probable cause” to believe the suspect has committed a crime, these lesser authorities require only “reasonable grounds” to believe the information sought would be “relevant” to some legitimate investigation. That is, needless to say, a far lower hurdle to meet.

Police refusal to discuss the program with reporters is also part of a larger pattern of secrecy surrounding location tracking. As Magistrate Judge Stephen Smith observes in a recent and important paper, such orders are often sealed indefinitely—which in practice means “forever.” Unlike the targets of ordinary wiretaps, who must eventually be informed about the surveillance after the fact, citizens who’ve been lojacked may never learn that the authorities were mapping their every move. Such secrecy may be useful to police—but it also means that improper use of an intrusive power is far less likely to ever come to light.

Location tracking can be a valuable tool for an array of legitimate law enforcement purposes—but especially in light of the Supreme Court’s unanimous decision in United States v. Jones, it has to be governed by clear, uniform standards that satisfy the demands of the Fourth Amendment.