Today the U.S. Supreme Court will hear oral arguments in what may prove to be one of the most significant Fourth Amendment cases in years.

The Fourth Amendment, of course, famously guarantees "the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures." Yet according to the Supreme Court's 1979 decision in Smith v. Maryland, "a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties."

Otherwise known as the third-party doctrine, this legal rule has proven quite valuable to law enforcement agencies over the past four decades. Perhaps the police would like to learn the URLs of the websites that someone has visited, or perhaps learn the email addresses that someone has corresponded with? The third-party doctrine lets the police obtain that information without first obtaining a search warrant for it.

But doesn't the idea of granting vast warrantless search powers to the police run afoul of the privacy protections enshrined in the Fourth Amendment?

The Supreme Court will grapple with that question today when it hears oral arguments in Carpenter v. United States. At issue is whether the FBI violated the Fourth Amendment when it obtained, without a search warrant, the cellphone records of suspected armed robber Timothy Carpenter. With those records, law enforcement officials identified the cell towers that handled his calls and then proceeded to trace back his whereabouts during the time periods in which his alleged crimes were committed. That information was used against Carpenter in court.

According to Carpenter and his lawyers, "carrying a smartphone, checking for new emails from one's boss, updating the weather forecast, and downloading directions ought not license total surveillance of a person's entire life."

According to the Trump administration, "a cell-phone user has no reasonable expectation of privacy in business records created by his provider documenting the cell sites used to document his calls."

What will the Supreme Court do? Will the justices rework the third-party doctrine, cabin the power of the police, and recognize broad Fourth Amendment protections for the digital age?

At least one member of the Court seems inclined to do just that. As Justice Sonia Sotomayor remarked in the 2012 case of United States v. Jones, "people disclose the phone numbers that they dial or text to their cellular providers; the URLs that they visit and the e-mail addresses with which they correspond to their Internet service providers; and the books, groceries, and medications they purchase to online retailers…. I would not assume that all information voluntarily disclosed to some member of the public for a limited purpose is, for that reason alone, disentitled to Fourth Amendment protection."

We'll find out later this term whether or not a majority of the Court shares Sotomayor's welcome view of the Fourth Amendment.