My understanding is that the ruling hinges on the physical attachment of the GPS tracker to a person's effect (their car) being a violation of the fourth amendment. The first two pages have a concise summary.

I don't see how that would apply here.

Sotomayer, Alito, Ginsburg, Breyer and Kagan concurred with the original decision, but wrote separate decisions bring up these exact points.

> Sotomayer, Alito, Ginsburg, Breyer and Kagan concurred with the original decision, but wrote separate decisions bring up these exact points.

Strictly speaking, only Sotomayor concurred in the original decision, Alito, Ginsburg, Breyer, and Kagan concurred in the judgement (that is, the result).

The difference is significant in general, because the decision includes the rationale, and the Alito opinion (joined by Ginsburg, Breyer, and Kagan) disagrees with the rationale of the majority opinion. (That is, the majority held trespass to be decisive, Sotomayor agreed that it was in this case, but explicitly wrote a concurrence to argue that trespass wasn't necessary for a violation, and the other four agreed that GPS was a violation, but disagreed that trespass was an appropriate consideration.)

That is, there were four justices who believed that the GPS tracker was a violation because of the trespass to the target's property, four justices who though it was a violation for other reasons, but not because it was trespass to property, and one who thought it was violation because of trespass to property as well as other reasons.

Which results in the interesting situation, in that there were different (but overlapping with Sotomayor in both) 5-vote majorities both for the violation due to trespass view and the violation due to reasons-other-than-trespass view.

> Sotomayer, Alito, Ginsburg, Breyer and Kagan

One of these things is not like the others. Did Alito take the same position as the others listed here?

Basically. Sotomayer wrote one concurring decision, Alito wrote the other, and the rest were with Alito. Alito's not all bad; this decision really brought out the anti-government side of him.

So basically instead of a GPS tracker, they could have an autonomous silent drone follow a few feet behind the vehicle instead, and that wouldn't violate the ruling.

Yes, the police doesn't need a warrant to tail you, question any one you speak too, or even use public systems to gain information on you, heck they technically don't even need in some cases a warrant to say get your phone records or any other record from any other person or company (they do need consent which is more often than not the actual reason behind a warrant being filed in the first place as it solves that issue).

They may not however tamper with your personal property.

If you do not own the car and say it's a company car the police might also not need a warrant to put a GPS tracker on it if they get consent from your employer, this might also cover rental cars (not sure about leases).

Is a passerby or member of the general public allowed to attach a camera to a utility pole? Last I checked, even putting flyers on utility poles in most municipalities is technically not allowed, even though they usually let you get away with it.

That to me would be a pretty clear line between a passerby and law enforcement in this case.

I found an interesting comment on Arstechnica's reader comments:

"I'm curious: would they need a warrant to sit in a car outside someone's house to watch them? " -Zak

At some point it may become stalking in a lot of states if they have no warrant.

No it doesn't, it can however be used to file a harassment or abuse of power law suit against the officers / police department / DA.

The police doesn't need a warrant for most things they due in their line of duty, most warrants are requested to compel instead of risking seeking consent not because the law mandates judicial approval.

"No it doesn't"

This is true but not for the reason you cite. It would be stalking if they make a statement that will place the person in reasonable fear of harm. If they did that, in most states, it won't matter whether they are doing it as cops or not. Some states have "no lawful justification" in the text (which would protect police), but most don't.

Various states do have laws that would cover this that are not stalking (violations of various invasion of privacy, wiretapping, etc).

Most are written in the way that it will be unlawful even if they are police.

Attaching something to the car quite literally violates "the right of the people to be secure... in their effects."

The Constitution however says nothing about "in their movements" or "in the light they reflect."