Technically they didn't, but interpreting how Jones will be used going forward is like reading tea leaves. Technically the Supreme Court, in Jones, ruled that altering a car in order to track its location constitutes a search. On this matter, five justices (Roberts, Scalia, Thomas, Kennedy, and Sotomayor) agreed to rule narrowly and put off any decisions on wider surveillance for another day. Scalia's opinion of the court makes it clear that it is not deciding any issues beyond that. Sotomayor's concurrence agrees.<p>Beyond that point, things become a bit tricky. Alito filed a concurrence in judgement (meaning he reached the same decision on different grounds) arguing the GPS tracking was a search because it was too intrusive in terms of the information collected and therefore violated a reasonable expectation to privacy. Kagan, Breyer, and Ginsberg joined him.<p>If that were the end of the matter, that would not make things hard at all, but then we have to come back to Sotomayor's concurrence. In her concurrence she expressly agreed that <i>although</i> the case was disposed of narrowly with her support, she <i>also</i> agreed with the concurrence in judgement that it violated reasonable expectation of privacy, so in this she endorsed the minority opinion <i>after</i> joining the majority which is why this is tricky to make sense of.<p>At very least, the fact that 5 justices appear to agree that this is a problem gives circuit courts permission to experiment with rationales as to why this is the case. It is however premature to say that the Supreme Court has so <i>ruled.</i><p>To recap, you have three opinions in Jones:<p>Opinion of the court (Scalia, joined by Roberts, Thomas, Kennedy, and Sotomayor): Reasonable expectation to privacy is not the only test of the 4th Amendment. When there is a common law trespass there is always a search. We need not decide whether this violates reasonable expectation to privacy because we can rule this was a search due to the trespass.<p>Concurring in judgement (Alito, joined by Breyer, Ginsberg, and Kagan): This surveillance violates the 4th Amendment due to its intrusiveness and the level of information obtained. People have a reasonable expectation to privacy that is violated by massive surveillance of this sort.<p>Sotomayor, concurring with Scalia: I join Scalia in ruling on narrow grounds, but I also think that Alito is right....