From Ferguson to Senate hearings, the news of local police arming themselves with federal-grade equipment—tanks, riot gear, M16 rifles—has captivated everyone from civil libertarians to lawmakers. But in the national debate surrounding police militarization, the most effective weapons may have been overlooked: Beyond arming themselves like the federal government, local police are also spying on you like the federal government—using sophisticated surveillance technology without warrants.

One of the tools making it possible for Chief Wiggum to gather all your deets is known colloquially as a Stingray, a portable gadget about the size of a box of doughnuts. They’re also known as “cell-site simulators,” because, well, that’s exactly what they do: A Stingray mimics a cellphone tower and forces all nearby mobile phones or devices to connect to it. Every phone that connects to the Stingray reports its number, GPS location, and the numbers of all outgoing calls and texts. That’s every location and outgoing call and text log of every phone within a certain radius—up to several kilometers—of the Stingray, and that’s all without a warrant.

It’s probably not a huge surprise to most people in America today that the federal government has incredible surveillance technology that it uses occasionally on its own citizens. (Hi, NSA!) But polling shows that only 27 percent of people think that this technology is focused on them, and even if not, half of Americans surveyed say that there might be a margin of federal surveillance they’re willing to endure in the name of homeland security or fighting terrorism.

But that logic is a much harder sell when it comes to local police, who have been acquiring Stingrays in increasing numbers. At least 46 state and local police departments, from Sunrise, Florida, to Hennepin, Minnesota, have gotten cell-site simulators, which range widely in price from $16,000 to more than $125,000 a pop. And like the federal government, local police are using this technology without any judicial oversight. That means Barney Fife—or, if you’re looking for a more sinister example, think Denzel in Training Day—can walk into your neighborhood with a Stingray, fire it up, and collect all the numbers, GPS, and call logs of every cellphone in the area. If they’re looking for a specific number (hopefully, it’s not you), they can also use a Stingray to trick your phone into being a personal GPS tracker and then use that warrantless cellphone tracking to enter your home and arrest you—again without a warrant.

At least that’s what happened to James Thomas in 2008 when local Tallahassee police in pursuit of a stolen cellphone taken during an alleged assault tracked the device to his apartment building with the use of a Stingray. Police then went door to door in the apartment building until they located the apartment that they believed the signal was coming from. When Thomas’ girlfriend answered the door and refused entry, police pushed her aside, entered the apartment, and arrested Thomas.

Absent certain extreme circumstances, police can’t enter a person’s home without a search warrant. In Thomas’ case, police had not gotten a warrant to track the stolen phone using the Stingray. And though the tracking info gained from the Stingray might have provided an underlying basis for a judge to issue a warrant for Thomas’ apartment, police refused to tell how they had tracked the phone to Thomas—likely because they weren’t in a hurry to disclose the warrantless use of a stealth surveillance device without a warrant in the first place. So it wasn’t until 2014, six years after Thomas’ arrest, that his lawyers found out that a Stingray had been the basis for entering Thomas’ apartment. In reversing the trial court’s finding that the search was lawful, two Florida state appeals judges terrifyingly noted in oral argument that the Stingray technology used to track and arrest Thomas had been employed over 200 times by the local police without a warrant.

The lack of warrants is striking in Thomas’ case, but it had even more daunting results in the case of Louise Goldsberry. According to a civil complaint filed in the middle district of Florida, in July 2013 Goldsberry, 59, was standing at her kitchen window when she observed armed men surrounding her apartment. Ducking behind the sink, she crawled to her hallway and armed herself. She then heard knocking and demands to “open the fucking door.” When she demanded identification, she received no reply. The men opened the door, entered her home, and demanded at gunpoint that she put down her weapon. After finally identifying themselves as police—and never producing a warrant—they removed Goldsberry from her house, handcuffed at gunpoint, while they searched her home. The basis for the search was a Stingray device. Unfortunately for Goldsberry, the phone and the man the police they were looking for was located in a nearby unit in her building.

The problem with Stingrays is twofold. Goldsberry’s case illustrates the first: Stringrays simply don’t provide reliable results—if a cellphone is located near a wall separating two apartments, it is nearly impossible to determine which apartment that phone is in.

But perhaps the larger and scarier problem with Stingrays is that they now give local police all of the information that any particular cell tower has, without having to bother with a subpoena to cellphone companies. It’s this dragnet aspect of Stingrays—that police can simply drive to neighborhoods and log calls, numbers, and locations—that has a terrifying effect on privacy. It’s easy to imagine the parade of horribles that could result from this type of continued used of Stingrays without warrants by local police: targeting and tracking of certain protesters, or a more general dragnet collection of phone numbers in high crime areas, or even use by one local police officer who has a grudge. Both of these issues are problems that judge-issued warrants—which require a level of specificity and basis for the particular search that a reasonable human being must accept—were designed to solve.

But warrants can’t solve the problem if something isn’t considered a search under the Fourth Amendment in the first place, and so far Stingrays seem to be escaping through this loophole. Few courts have ruled on whether Stringrays constitute searches, though all signs suggest they would be. The Supreme Court has slowly (emphasis on the slow) but surely been updating the Fourth Amendment to comport with existing technology.

Most recently, in United States v. Jones, the court found a GPS tracker placed on a suspect’s car for four weeks was a search, reasoning that the long-term surveillance and collection of data was a violation of Jones’ reasonable expectation of privacy. But Jones didn’t answer the question of whether electronic collection of data—say from cellphone companies or Stingray devices—which doesn’t physically intrude on a suspect constitutes a search. In the void of rulings on the topic, police are either going ahead with their dragnet Stingray searches without notifying judges at all, or are failing to disclose that they’re using Stringrays on their requests for warrant applications.

In the interim, groups like the American Civil Liberties Union and the Electronic Frontier Foundation are working to pass statutes requiring disclosure and transparency by the police when they use and request warrants for the use of Stingrays. “In order for warrants to meaningfully constrain police action, the government must be candid with judges about when it intends to use Stingrays and what Stingrays’ capabilities are,” says Nathan Wessler, an attorney at the Speech, Privacy, and Technology Project at the ACLU. “Without that information, courts simply cannot ensure that the government is complying with the Fourth Amendment.” So far 11 states—Colorado, Illinois, Indiana, Maine, Maryland, Minnesota, Montana, Tennessee, Utah, Virginia, and Wisconsin—have passed laws that require police to get a warrant to use a Stingray.

In the courts, action is taking the form of public access and suppression motions. In Arizona, the ACLU is suing the Tucson Police Department and has filed amici briefs in other cases in the state. Similarly, in Florida, public access motions have been filed in Sarasota to unseal all court orders related to police Stingray use. It appears that some progress is being made: In mid-October, the Florida Supreme Court held in Tracey v. Florida that a warrant is required for real-time cellphone location tracking carried out at police request by the cellphone service provider. Advocates are hopeful that this might be the bridge needed after Jones and that the opinion will apply to Stingray use as well.

But until that happens, the silent use of Stingray technology and the lack of public knowledge or oversight about their use continue to be a danger. Just this month, the Washington Post reported that Prince George’s County, Maryland, bought a Stingray using civil asset forfeiture funds. Unlike tax dollars, the use of civil asset forfeiture funds has no democratic oversight. “In other words,” says Wessler, “it just keeps making it easier for Barney Fife to act like Barney Fife.”

This article is part of Future Tense, a collaboration among Arizona State University, New America, and Slate. Future Tense explores the ways emerging technologies affect society, policy, and culture. To read more, visit the Future Tense blog and the Future Tense home page. You can also follow us on Twitter.