For award-winning Canadian photojournalist Ed Ou, his October 1st trip to the United States started out like any other assignment. But while his plan was to cover the Standing Rock protests for the CBC, he never got past the US border agents.

Ou is no stranger to run-ins with foreign authorities. According to the Columbia Journalism Review, he’s been detained or arrested in Turkey, Egypt, Somalia, Djibouti, and Bahrain. But he never expected that same treatment in the USA.

As first reported in The Washington Post, Ou was on assignment for the CBC, on his way to cover the Standing Rock protests as part of a long-term project about health care for indigenous people in North America. But when he got to the border, he was detained and interrogated for over 6 hours, had his journals photocopied, documents confiscated, and his phones tampered with.

Ultimately, Ou, a photojournalist who has been published in The New York Times, Harper’s, TIME, and many others, was denied access into the country and told not to try again. In the end it was revealed to Ou that he was on some sort of “person of interest” list, and that the details are classified.

Journalistically speaking, the main concern Ou and the CBC have is the warrantless phone search. As The Washington Post points out, if Ou had been in the US, officers would have needed a warrant to search his phones. No such protections exist at the border. It’s unclear if any sources were compromised—Ou encrypts his phones by habit when he’s crossing a border—but it’s certainly possible.

The ACLU, which is helping Ou respond to this issue with Customs and Border Projection (CBP), called the search “unjustified and unlawful.” They are demanding that the government destroy any copies of Ou’s data, explain why he was stopped in the first place, and assure the journalist that he won’t deal with similar treatment in the future.

Image credits: Public domain photograph by U.S. Customs and Border Protection.