The US Department of Homeland Security said Yiannopoulos was returned to his home country on Friday after being accused of overstaying after entering the US legally in May 2019.
A immigration judge had issued a final order of removal on July 22 after he failed to show up for an immigration hearing, a Homeland Security spokesperson said.
Yiannopoulos was arrested on Thursday at Louis Armstrong New Orleans International Airport in Louisiana and detained by Immigration and Customs Enforcement.
"He chose to overstay his welcome in violation of our nation's laws," a Homeland Security spokesperson said in a statement.
Yiannopoulos and his representatives did not respond to requests for comment. He has not posted on his X social media account since Thursday.
Yiannopoulos is a well-known champion of conservative causes and has frequently taken provocative public positions criticising feminism, Islam and immigrants. He has been especially supportive of President Donald Trump's immigration crackdown.
"Zero immigration for the next 20 years. No ifs, no buts," Yiannopoulos wrote on X last year.
The British national has most recently worked for the rapper Ye, formerly known as Kanye West, who performed in New Orleans on Friday evening.
Yiannopoulos rose to fame in the early 2010s as an incendiary writer for the conservative website Breitbart News.
He resigned from the company in 2017 after a video of him endorsing pedophilia resurfaced online. He later apologised for the remarks and said he himself was a victim of sexual assault as a minor.
Yiannopoulos' arrest on Thursday comes amid a nationwide uptick in detentions as part of Trump's immigration crackdown.
Far-right conservative activist Laura Loomer swiftly took to social media to applaud Yiannopoulos' arrest after years of public feuding between the two personalities.
"I was the first person to report on the fact that Milo was in the US illegally where he incited violence against President Trump and worked for Marjorie Traitor Greene," Loomer wrote on X.
Controversy around Yiannopoulos ballooned in 2017 when he carried out what he called his "Troll Academy Tour" across college campuses nationwide.
Fights broke out when some students protested Yiannopoulos' appearances and accused him of hate speech, while others celebrated him as a champion of free speech. Around that time, Buzzfeed reported on Yiannopoulos' cozy relationships with self-proclaimed white nationalists.
In recent years, Yiannopoulos continued to work in the orbit of conservative activism.
Most recently, Yiannopoulos has worked as a spokesperson for Ye, who has been beset by controversy of his own following anti-Semitic comments that the rapper has since apologised for.
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