Justice Sonia Sotomayor then writes, agreeing with Scalia’s trespass approach, but adding in a separate concurrence for herself alone, that actually anticipates being read by light bulb as opposed to flickering taper. Even though she’s looking forward and not backward, for Sotomayor, Scalia’s trespass-based approach is the better one: “When the Government physically invades personal property to gather information, a search occurs. The reaffirmation of that principle suffices to decide this case.”

Having said all this, Sotomayor then launches into a terrifying exposition about all the ways in which government surveillance no longer actually requires any physical intrusion, and she notes that Scalia’s majority opinion offers no future guidance for regulating such surveillance. Sotomayor cautions that new surveillance systems will fundamentally alter the relationship between government and citizens. She writes, “I would ask whether people reasonably expect that their movements will be recorded and aggregated in a manner that enables the Government to ascertain, more or less at will, their political and religious beliefs, sexual habits, and so on.” She goes on to warn about an even more worrisome violation of privacy when one’s personal information is voluntarily disclosed to third parties, noting, “I for one doubt that people would accept without complaint the warrantless disclosure to the government of a list of every Web site they had visited in the last week, or month, or year.” Because she joins on with Scalia’s majority opinion, however, these musings are—at least for now—just high-tech musings.