Well, the Court has just handed down its opinion in that case. SCOTUSblog has an excellent analysis of the opinion, which was only unanimous to the extent that all the justices agreed with the appellee’s contention that the use of this wireless GPS device to track his vehicle violated his Fourth Amendment rights.
The justices disagreed, however, on exactly what “Fourth Amendment rights” meant in this case. The majority opinion (Scalia, Roberts, Kennedy, Thomas, Sotomayor) was the narrowest and seems to mostly stand for the proposition that law enforcement agencies would be well advised to get a warrant before doing this sort of thing, but it stops short of holding that a warrant is categorically necessary. They essentially held that the physical intrusion of the device on the car was a “search” but punted on the use of the technology. The four-justice concurring opinion (Alito, Ginsburg, Breyer, Kagan), wanted to talk more about whether or not there was a reasonable expectation of privacy with respect to the use of GPS tracking and suggested that the longer the tracking goes on, the more of an expectation there is. Sotomayor also filed her own concurring opinion which actually criticizes the majority opinion—which she joined—suggesting that if the cops try to get too funky with warrantless, wireless tracking, she may well side with the other bloc of justices and opt for a ban.
While we certainly didn’t predict how this was going to play out in terms of the justices voting patterns, this is basically what we predicted would happen overall. As we said, “The Justices seem likely to say that while there isn’t necessarily a reasonable expectation of privacy in one’s movements in public places, the police still can’t directly track your movements without either your consent or a warrant.” So ultimately, the Court didn’t decide the former issue but suggested that the latter is probably true. At the very least, using a physical device attached to one’s person or property now constitutes a “search” under the Fourth Amendment.
So this isn’t precisely a “retcon” as much as it is an update. The original post suggested that Batman probably needed a warrant to use that tracer on Bob Cratchit, and today’s opinion in Jones says that this is correct.