“The Fourth Amendment … Is In Retreat”

That’s how a dissenting opinion ends in a major federal case that was decided on Tuesday. This is how it begins:

“A customer buys a cell phone. She turns it on and puts it in her pocket.”

And with that, according to the majority’s opinion, the customer has consented to create a record of everywhere she goes, a record which the government can then obtain without a search warrant based on probable cause.

Neat trick, huh?

If the government wanted to plant a tracking device on you to follow you everywhere you went, it would need a warrant, but if it wants to let your cell phone do the work, it doesn’t.

Instead, under a federal law from 1986, it can apply for a special order to get your phone’s cell-site location data. These are the logs of cell towers that your phone connects to as you go about your business. They create a fairly precise record of where your phone goes.

The special order must be approved by a judge, but the government doesn’t have to show probable cause to believe you committed a crime; it only needs to show reasonable grounds to believe that your travels are “relevant and material to an ongoing criminal investigation.” Off the top of my head, I can’t think of a case where the government couldn’t argue your travels were important once it decided to investigate you for something.

In this case, the government obtained seven months’ worth of records this way.

On appeal, the court not only denied that the Fourth Amendment required a search warrant backed by probable cause, but it denied that the Fourth Amendment applied at all because, supposedly, you have no reasonable expectation of privacy in data that you share (or that your phone shares) with a third party such as your cellular service provider.

The court didn’t explain how people are supposed to work, date, or otherwise live in the real world without doing so.

As we’ve noted before, this third-party doctrine makes no sense in the digital age.

Fortunately, many states, including California, are going the other way.