None of these differences makes a difference, though. Whether a person has a cognizable privacy interest in some piece of property or information has nothing to do with whether the police have a legitimate interest in him. You either have a protected privacy interest in something or you do not. The police need particularized suspicion and judicial permission to collect that something only if you have such an interest. If you do not, the police do not need suspicion or permission — no more than I needed them before thumbing through the phone book when I was a prosecutor.

The Supreme Court reasoned that you do not have a privacy interest in third-party records of your phone usage because you well know that your usage information is not private. As the justices put it, at the time you make any call, you are knowingly “conveying” that information to the phone company. That rationale has nothing to do with whether you are a crime suspect. And that rationale does not change based on whether the government is collecting usage records for one phone number or for 300 million.

There is no cognizable property interest or expectation of privacy, so that is the end of the matter as far as the Constitution is concerned. It should therefore be the end of Senator Paul’s lawsuit. But, as discussed above, it does not settle the question of statutory legality, much less the question of whether the policy, even if lawful, is an excessive intrusion on privacy.