French scientist denied entry to United States after criticizing Donald Trump - here are the grounds for the denial
There are a few reasons a foreigner may be denied entry into the United States, and criticizing the president may fall under one of the more obscure.


A French scientist was on his way to a conference in Houston, Texas on March 9, when he was subjected to a random search at the airport. Officers took his belongings and searched through his phone, finding “hateful” messages toward President Donald Trump.
Authorities confiscated both his personal and professional equipment. The space researcher was then denied entry into the states and sent back to Europe the following day.
Le Monde/AFP reporting that a French scientist, who came to Houston for scientific conference, was expelled after random search turned up electronic messages highly critical of Trump. https://t.co/YB6YokYvd0
— Roger Parloff (@rparloff) March 19, 2025
The reasons someone can be denied entry to the U.S.
If you’re wondering if this is actually legal, the answer is yes. There are many reasons why a foreigner could be denied entry into the United States: Criminal admissibility, insufficient funds, medical inadmissibility, lying, suspicious activity, drug use, intent to immigrate illegally or work illegally, improper documentation, and previous denial of entry.
In the case of this French scientist, he would fall under the “suspicious activity” category, which is quite an ambiguous one. All denials are left to the discretion of border agents and the CBP at large. They do have the right to ask for your devices as well as passwords to social media accounts. Suspicious activity can include anti-government sentiment. In fact, some travelers will scrub their accounts prior to traveling for that reason.
The officers who searched the Frenchman’s phone said they found messages “which conveyed a hatred toward Trump and could be considered to be terrorism”. The FBI opened an investigation into the matter, but later dropped the charges.
France minister of higher education and research condemns U.S. authorities
France’s minister of higher education and research, Philippe Baptiste condemned the authorities for denying the researcher entry into the U.S.
“I learned with concern that a French researcher who was traveling to a conference near Houston was denied entry to the United States before being expelled”, Baptiste said on Monday. “This measure was apparently taken by the American authorities because the researcher’s phone contained exchanges with colleagues and friends in which he expressed a personal opinion on the Trump administration’s research policy.”
“Freedom of opinion, free research, and academic freedom are values that we will continue to proudly uphold. I will defend the right of all French researchers to be faithful to them, while respecting the law,” Baptiste said.
That same day, Baptiste, who has also been openly critical of Trump as well as Elon Musk, called on American researchers to consider relocating to France, citing dissatisfaction with the U.S. research environment under the Trump administration as well as scientific budget cuts.
Trump is defying court orders and abusing wartime powers to deport people with no due process.
— Elizabeth Warren (@SenWarren) March 17, 2025
He's using the law that put Italian, German, and Japanese immigrants in detention camps during World War II.
We are not at war. Donald Trump is not a king. He is not above the law. https://t.co/kX0DEhXs11
France’s Foreign Ministry also criticized the incident. They say that they value “freedom of expression” and suggested that the U.S. is “sovereign” when it comes to border control.
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