Here’s the description of one such product, available on Chinavasion:
small sized Anti GPS Tracking Device, powered by and for use with any car that has a standard Cigarette Jack for power and supplys 12V . Operation is incredibly easy, as all it take to work is plugging it into the cigarette lighter and it's on and working! The Anti-Tracker will knock out GPS logging or GPS tracking systems that may be operating on your vehicle. Using our Anti-Tracker will make it very hard for any one to keep tabs on you or your vehicle.So here’s the way criminals (and anyone else) can protect themselves from being tracked by GPS devices surreptitiously installed on their vehicles. As I’ve written before, courts have consistently, and correctly, held that under current Fourth Amendment law it is not a “search” to monitor such a device, one it has been installed in a “public” part of the vehicle (e.g., not inside, in the trunk, etc.). A few courts have held (incorrectly, IMHO) that it is not a “seizure” under current Fourth Amendment law to install such a device.
If this product works as it’s supposed to, that would eliminate the problem: Install the device in your vehicle and block any surreptitiously-installed GPS devices from tracking your movements.
As to whether the use of an anti-GPS device is legal or not, I don’t know. I did some quick research just now, being in a bit of a hurry to go somewhere, and couldn’t find anything that seems to criminalize its use. I did find cites to several cases in which courts approved law enforcement’s using certain tactics because the suspect was utilizing “anti-surveillance” technology, which frustrated their wiretapping efforts.
I know lots of people, including lawyers, who periodically have their offices swept for bugs, and that’s never been a crime, so I’m guessing the use of a device like this isn’t a crime, either. (Don’t take that as legal advice – it’s a rushed Sunday morning guess.)
The analogy that comes to mind is the use of radar detectors to try to avoid getting a speeding ticket. I know the use of radar detectors is illegal in some states (don’t know how many), but that’s different: You’re using the radar detector intentionally to facilitate your violating the law – the laws against speeding. So, since a radar detector’s only purpose is to facilitate the commission of illegal activity (granted, minor illegal activity, but it’s still illegal), it’s only logical to outlaw their use. (The other way to go would be to hole the manufacturers of radar detectors as accomplices to the crime they are facilitating, speeding, but that’s just silly.)
Unlike radar detectors, anti-GPS technology is not, itself, facilitating a crime. It’s a way to preserve your privacy . . . from police, from your spouse’s divorce attorney, from a jealous lover, from anyone you don’t want spying on you. Since you have a right to privacy, I can’t see why or how Congress or state legislatures could outlaw the use of this technology.
Some might argue that it is being used to commit a crime if it’s being used by criminals, but that argument only works if the anti-GPS technology itself is being used to commit a crime or to facilitate the commission of a crime . . . such as, say, a fugitive’s flight from justice. But I still don’t think you can outlaw it because, to continue with this example, someone who is fleeing from justice uses all kinds of things in the course of doing so: telephones, cars, airplanes, trains, hotels, etc. We don’t hold those who provide these products and services liable for facilitating the flight, so I don’t really see why that would work for the anti-GPS technology, either.