A French historian who has taught at the Sorbonne and Colombia University was detained by US customs for 10 hours yesterday.
Henry Rousso, 62, was on his way to a symposium at Texas A&M University when immigration officials at Houston airport decided he should be denied entry into the USA and be deported.
Officials felt that since Mr Rousso was going to be paid for participating in the symposium, the tourist visa he was travelling on was not valid.
"I confirm," he wrote on Twitter, "I have been detained 10 hours at Houston Itl Airport about to be deported. The officer who arrested me was 'inexperienced'".
It took 10 hours, Texas A&M University intervention and the services of an immigration lawyer to secure his release.
"Thank you so much for your reactions. My situation was nothing compared to some of the people I saw who couldn't be defended as I was," he subsequently wrote on Twitter.
Mr Rousso has written extensively about Holocaust-era France and is currently a senior researcher at one of France's largest public research institutes.
He was born in Egypt but moved to France aged two, after his family was expelled from the country in 1956.