If the government puts a GPS tracker on you, your car, or any of your personal effects, it counts as a search—and is therefore protected by the Fourth Amendment.

The Supreme Court clarified and affirmed that law on Monday, when it ruled on Torrey Dale Grady v. North Carolina, before sending the case back to that state’s high court. The Court’s short but unanimous opinion helps make sense of how the Fourth Amendment, which protects against unreasonable search and seizure, interacts with the expanding technological powers of the U.S. government.

“It doesn’t matter what the context is, and it doesn’t matter whether it’s a car or a person. Putting that tracking device on a car or a person is a search,” said Jennifer Lynch, a senior staff attorney at the Electronic Frontier Foundation (EFF)*.

In this case, that context was punishment. Grady was twice convicted as a sex offender. In 2013, North Carolina ordered that, as a recidivist, he had to wear a GPS monitor at all times so that his location could be monitored. He challenged the court, saying that the tracking device qualified as an unreasonable search.

North Carolina’s highest court at first ruled that the tracker was no search at all. It’s that decision that the Supreme Court took aim at today, quoting the state’s rationale and snarking:

The only theory we discern […] is that the State’s system of nonconsensual satellite-based monitoring does not entail a search within the meaning of the Fourth Amendment. That theory is inconsistent with this Court’s precedents.

Then it lists a series of Supreme Court precedents.

And there are a few, as the Court has considered the Fourth Amendment quite a bit recently. In 2012, it ruled that placing a GPS tracker on a suspect’s car, without a warrant, counted as an unreasonable search. The following year, it said that using drug-sniffing dogs around a suspect’s front porch—without a warrant and without their consent—was also unreasonable, as it trespassed onto a person’s property to gain information about them.

Both of those cases involved suspects, but the ruling Monday made clear that it extends to those convicted of crimes, too.

But much remains unclear about how the Fourth Amendment interacts with digital technology. The Court so far has only ruled on cases where location information was collected by a GPS tracker. But countless devices today collect geographic information. Smartphones often contain their own GPS monitors and can triangulate their location from nearby cell towers; electronic toll-collection systems like E-ZPass register, by default, a car’s location and when it passed through a toll road.

Lynch, the EFF attorney, said that the justices seem to know that they’ll soon have to rule on whether this kind of geo-locational information is protected.

She also said that those questions are more fraught for the Court than ones just involving GPS tracker data. Some members of the Court, including Justice Antonin Scalia, argue the Fourth Amendment turns on whether the government has trespassed on someone’s private property. Other members—represented in arguments by Justices Sonia Sotomayor and Samuel Alito—say that people have a reasonable expectation to the privacy of their location data.

For now, Monday’s ruling will force lower courts to consider whether attaching a GPS tracker to someone or something is a reasonable search, Lynch said. “It makes very clear to state courts and lower courts considering this issue that at least they have to get to that point,” she told me.

North Carolina isn’t alone in requiring past sex offenders to wear a GPS tracking device. Wisconsin also forces convicted sex offenders to wear location monitors for the rest of their lives, and Lynch said the EFF is looking at similar cases in other states. In her opinion, lifelong GPS tracking does constitute an unreasonable search. Her thinking: By the time they’re monitored, convicts have served their time and have theoretically repaid society for their crimes.

“They should have the opportunity to rebuild their lives and not be under a state of government surveillance for the rest of their lives, and that’s what a GPS tracker constitutes,” Lynch said. “Sex offenders—it’s the easiest class of people to place these kinds of punishments on, but I worry that we start with sex offenders and then we go down the line to people who’ve committed misdemeanors.”


* This article originally stated the name of the Electronic Frontier Foundation as the Electronic Freedom Foundation. We regret the error.