A lawyer representing a pro-Palestinian protester was detained Sunday at the Detroit Metro Airport on his way back from a spring break trip abroad with his family ― and federal agents tried to force him to turn over his phone.

Amir Makled says he stood his ground amid the ensuing 90-minute quarrel, as he argued that the sheer volume of privileged, work-related material on the phone prevented him from turning it over voluntarily.

He agreed to let the agents see his contact list, but he refused to provide any information about who the contacts were.

“I don’t know if it was a fishing expedition or not,” he told HuffPost. “My gut tells me they were trying to see who I was associating with. But there’s no real way to tell.”

In March, the Trump administration directed the Justice Department to target lawyers and law firms “who engage in frivolous, unreasonable, and vexatious litigation against the United States.”

Seizing an attorney’s phone ― or at least attempting to ― would seem to be in line with that directive.

So what’s Makled’s advice to people who may find themselves in a similar situation?

Have a designated device you travel with ― and one you leave at home.

“The government can take your phone at the border. It’s just something they’re allowed to do,” he said. “I don’t agree with that law, but there’s a statute that says they can take it and give it back to you later.”

Makled stressed that you don’t have to provide them with your passwords or walk them through what’s on your phone, but it’s legal for them to inspect the device itself. (HuffPost has a thorough explainer here with more information on what to do if a border agent asks for your phone.)

While he’s unsure what the agents hoped to glean from the device, it’s possible Makled was singled out because he’s representing Samantha Lewis, a student protester who was arrested last year after she participated in a pro-Palestinian protest at the University of Michigan.

Lewis and seven other protesters, all of whom are American citizens, are awaiting trial on a felony charge of resisting police officers that Makled argues represents a threat to freedom of speech.

“This is how authoritarian tactics start,” Makled told Michigan Public last month while discussing Lewis’ case. “Not by outright banning speech, but by making people afraid to exercise their rights.”

The government wants to send a message that if you speak out, there could be consequences, he said, “and they’re doing this to create this chilling effect so that they can discourage future activism. Then by the very nature of it makes it seem too risky for others.”