The Supreme Court on Wednesday morning will hear arguments in a major privacy controversy about police tracking people through their cellphones that may bring about permanent changes to how the courts interpret the Constitution’s Fourth Amendment.

At issue in Carpenter v. United States is the constitutionality of police's warrantless search and seizure of a cellphone user’s records to uncover that person’s location and movements.

The government obtained location data in 2011 on Timothy Carpenter, a suspected criminal in Detroit, without getting a warrant. Carpenter appealed to the 6th Circuit Court of Appeals, which ruled that the government did not need a warrant. Carpenter’s lawyer and the American Civil Liberties Union asked the Supreme Court to hear Carpenter’s case, and the justices agreed to do so in June.

The Carpenter case is one of the most anticipated cases of the high court’s current term in the technology and legal sectors. The U.S. Public Policy Council of the Association for Computing Machinery, the world’s largest computing professional society, said Tuesday it “considers this [case] a watershed moment” with “the legality of potentially indiscriminate government surveillance” at stake.

“The classical interpretation of the Fourth Amendment — previously viable — is now at odds with the realities of modern society,” said spokesman Jim Ormond. “Its interpretation must be brought into the current era. The alternative is that the Fourth Amendment, and the liberty interests found in the Fifth, will be rendered meaningless. As more personal information — and more sensitive information — is held by third parties, we must restore the historical balance protecting both the liberty of the individual and the interests of the government.”

Several of the nation’s largest tech companies, including Apple, Facebook, Google, Microsoft, Twitter, and Verizon, filed a brief in August urging the Supreme Court to strengthen the Fourth Amendment’s protections for consumers via the Carpenter case by changing the way the amendment is applied. The major technology companies did not expressly endorse either side.

Under current law, the federal government isn't required to obtain a warrant to get cellphone location information under what is known as the "third-party doctrine," derived from two Supreme Court decisions from the 1970s.

The Supreme Court said when a customer gives information to a third-party, such as a phone company, the customer has lost the expectation of privacy by voluntarily handing it over to that third party. That party, the Supreme Court said, can do whatever it wants with it, including giving it to the government.

In a preview of Carpenter for the American Bar Association, John Marshall Law School professor Steven Schwinn pointed out that it is hard to guess how the justices could resolve the case.

“The court itself has given us only a few clues in its more recent Fourth Amendment cases dealing with modern technologies,” wrote Schwinn, John Marshall Law School professor, in a preview of the case for the American Bar Association. “On the one hand … the court is concerned about lengthy and intrusive monitoring of a suspect’s movement and that it is sensitive to the vast amount of very private information on a cell phone. That bodes well for Carpenter. But on the other hand, these cases do not squarely address the government’s acquisition of information from a third-party provider, a key question in this case. If the court applies a rigid third-party rule, that may bode well for the government.

“In any event, if the court rules that the government’s acquisition is not a ‘search’ under the Fourth Amendment, it will have to do some very careful line-drawing in order to account for the ruling’s application to now-unknown advances in technology.”

Orrin Kerr, George Washington University law professor and former law clerk to Justice Anthony Kennedy, called the Carpenter case “probably the biggest Fourth Amendment case that the court has had in at least five or six years, maybe longer.”

Kerr also noted that the Supreme Court agreed to hear the case without a split in the lower federal appeals courts and that none of the justices were on the high court when it last handled the precedents at issue in Carpenter.

After the justices hear arguments in Carpenter, they will prepare to tackle two major cases involving sports betting and the tension between free expression and gay rights next week.