I can understand people's aversion to this, and it's definitely bad policy, but it does not violate the 4th Amendment. It is neither a search nor a seizure.
Technically speaking, I could argue that it does violate the Fourth:
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
You could make a strong case that the government planting something foreign onto a citizen's property falls into the same category as searches and seizures, although I admit it's not explicitly included in the wording (in any case, it constitutes tampering with private property without a warrant). It does seem implicit though, which brings to mind the Ninth Amendment. After all, one of the reasons the Fourth Amendment exists is to prevent cops from planting evidence and then "finding" it. It seems a bit absurd to me to consider only the "finding" of evidence a violation of rights, and not the act of planting of foreign objects on private property itself. Illegally planting a GPS tracker to get evidence on a person's position and moving patterns is very much akin to planting a camera to get evidence on a person's actions - and because evidence later found on such a camera would in fact be considered an illegal search and seizure, I believe the same principle applies when police are illegally obtaining evidence on a person's position and movements by planting a tracker.
The problem is that it's not enough to say that illegally obtained evidence cannot be used in court (and the Fourth Amendment does not in fact limit itself to saying that). Sure, that helps, but that's not the end of the story...cops very often obtain evidence on a person through an illegal search and seizure, but fully knowing they can't directly use it in court, they'll go ahead and use the illegal evidence as a lead to find other supposedly "legal" evidence that can be used in court. However, the Fourth Amendment does not solely protect against illegally obtained evidence being used in court; it is meant to protect against cops illegally searching and seizing whatsoever! Because of that,
any of the fruits of those searches and seizures, whether direct or indirect, are equally illegal. Of course, it's not always easy to prove in all cases, but it seems like a no-brainer to me that cops cannot legally plant a GPS tracker without a warrant.
If someone is illegally tampering with
my car to keep track of (spy on) my person and my property, that could be considered a never-ending search of me and my property, even though the search does not go inside of my car or inside of my body with a cavity search. Besides, putting a tracking device on someone's car, especially without their knowledge, is an obvious violation of property rights...especially considering that violation is being used for the purpose of espionage.
The ironic thing is, when cops use illegal tactics like this, they're breaking much more serious laws and becoming much more serious criminals than a lot of the people they're going after. It seems absurd to me that so people always side with police over "criminals" (even entirely nonviolent drug offenders) and give the police the benefit of the doubt, even when the police
are criminals...and quite frankly, I believe that the more powerful you are compared to your victims (such as the government committing crimes against individuals), the greater and more heinous your crime should be considered.
