David Lapan, a spokesman for the Department of Homeland Security, said he could not comment on pending litigation but that “we absolutely believe the searches are lawful.”
In March, Joseph B. Maher, the acting general counsel for the agency, defended the practice in a USA Today opinion piece.
“These electronic media searches have produced information used to combat terrorism, violations of export controls, and convictions for child pornography, intellectual property rights violations and visa fraud,” he wrote. “This authority is critical to our mission, and Customs exercises it judiciously.”
While police officers on the street cannot compel you to hand over your phone without probable cause, border agents can search and confiscate digital devices as easily as they can your luggage. Courts have long held that customs officials have an interest in enforcing immigration laws and keeping contraband out.
But at least one major judicial case has acknowledged that cellphones are not the same as suitcases. In a 2014 Supreme Court decision that made it harder for police to search cellphones without a warrant, Chief Justice John G. Roberts Jr. wrote that the devices contained “the privacies of life.”
The policies that direct border agents are written to allow the digital searches “with or without individualized suspicion.” But it’s not clear what, exactly, border agents are searching through when they seize devices.
In June, Kevin McAleenan, the acting commissioner for Customs and Border Protection, wrote in a letter to lawmakers that agents are not permitted to look at data stored solely in the “cloud.” According to the letter, which was first reported by NBC News, agents would be limited to data stored directly on the device, including photos, text messages, call histories and contacts.
Esha Bhandari, an A.C.L.U. staff attorney, said in an interview that it was unclear whether agents would be permitted to search cloud-based apps on the phone, which would include social media accounts and email.
“We don’t think it changes anything with respect to the constitutional claims at issue here, which is that the government needs to get a warrant before it searches devices,” said Ms. Bhandari.
The Knight First Amendment Institute at Columbia University filed Freedom of Information Act requests in March to learn how the government was using its authority, but said that so far it has received only heavily redacted reports.
Jameel Jaffer, the institute’s executive director, said that the searches could have a chilling effect on journalists, lawyers and doctors, who often travel with their devices and have a professional obligation to shield the identities of their sources, clients and patients and the information they provide.
“It’s hard to see how the kind of unfettered authority that border agents have been invested with can be reconciled with the limits the constitution places on government power,” Mr. Jaffer said.
Of the 11 people who filed the lawsuit, 10 are American citizens and one is a permanent resident. They include journalists, students, a NASA engineer and an artist.
While the government cannot compel travelers to unlock their phones, several of the plaintiffs said they were intimidated. Four of them said their devices were confiscated; one of them, Suhaib Allababidi, a business owner from Texas, said the government kept an unlocked phone of his for two months, and hadn’t returned a locked phone after more than seven months.
Ms. Maye, an assistant professor of homeland security at Embry-Riddle Aeronautical University, said she was detained at the Miami International Airport on June 25 as she returned from a European vacation. She was brought into a small room and watched as a border agent briefly inspected her laptop then took her phone for about two hours, she said.
Ms. Maye said she was interrogated about her travels, career and contacts in the Middle East; she wrote her dissertation on Iraqi politics after the fall of Saddam Hussein and worked in Iraq for a year and a half on a United States government contract, she said. She still serves on a panel of academics that advises the United States Central Command.
She complied when agents asked her to unlock her phone because “I felt I had no choice,” she said.
“As someone who typically obeys people in authority, I did as I was told under the idea that they had Americans’ best interest in mind,” she said.
But as time went on and she was unable to communicate with her waiting husband, she became concerned about the thousands of emails, text messages and photos and the bank account information she had on her phone.
“Above all, I worried that my privacy was going to be violated at some point,” she said.