The American Civil Liberties Union contends U.S. customs agents should have to obtain search warrants before they rifle through travelers’ electronic devices at border crossings.

The ACLU, in an amicus brief filed Monday, urged the U.S. Court of Appeals for the Fourth Circuit to “hold that searches of portable electronic devices may not be conducted without a warrant or, at an absolute minimum, a determination of probable cause,” by Customs and Border Protection agents.

The Fourth Amendment, which gives people the right against unreasonable searches and seizures, doesn’t apply at the border. Customs agents assert they have the authority to search all electronic devices at the border, “no matter your legal status in the country or whether they have any reason to suspect that you’ve committed a crime,” according to the ACLU.

“We are urging the court to hold that the Fourth Amendment requires a warrant, or at minimum a probable cause, to search electronics because of the huge amount of personal information they contain,” the ACLU lawyer Esha Bhandari told The Huffington Post.

The brief was filed in a case involving a Turkish citizen convicted last year of trying to enter the U.S. with gun parts. Authorities seized his iPhone during the search. Bhandari said the ACLU’s brief is not to defend the Turkish citizen, but to remind the courts about the potential for government overreach.

“The goal of ours is to have the court think about the implications of ruling in this case for hundreds of millions of other travelers,” Bhandari said. “We want to urge the court ― regardless of whether evidence is warranted enough for this defendant ― to address squarely the Fourth Amendment question.”

The ACLU filed a similar brief in 2015, but that case was dismissed before the appeals court could decide whether warrantless border searches are legal.

Customs agents sometimes use their broad authority to inspect electronic devices belonging to travelers who may not appear to arouse suspicion of wrongdoing. Last year, a Wall Street Journal reporter said she was detained and asked to hand over her cellphone at Los Angeles International Airport.

Border agents detained a Canadian photojournalist for more than six hours as he traveled to cover to the Dakota Access Pipeline protests in October. Ed Ou, 30, told The New York Times the agents asked for his phone to look through his photos so that they could make sure he wasn’t “posing next to any dead bodies.” He was ultimately denied entrance into the U.S.

The reach of Customs and Border Protection extends to domestic flights as well. In February, federal agents demanded passengers arriving in New York show their identification as they searched for an immigrant who had received a deportation order to leave the country. The person they were seeking was not on the flight, according to The Washington Post.

On Monday, the U.S. banned laptops, tablets and other electronic devices in the cabins of flights from nine airlines operating in parts of North Africa and the Middle East. Meanwhile, President Donald Trump has twice attempted to ban travelers from certain Muslim-majority countries from entering the U.S. Those bans have been temporarily blocked by federal courts.