The split in reasons did lead to the fundamental question being sort of dodged. The majority opinion decided the case on quite narrow grounds: that the physical installation of the GPS device violated the 4th amendment, because installing it involved tampering with someone's personal property (the car) without a warrant. Four justices would have gone further and argued it would require a warrant to operate such a GPS tracker regardless of how it was installed, but the majority left that question unanswered.