Trump administration officials admitted that Columbia student Mahmoud Khalil was arrested without a warrant. Khalil, a green card holder, has been detained since March, when Secretary of State Marco Rubio cancelled his visa over nebulous allegations of "pro-terrorist" speech.

Khalil, 30, was the first international student arrested in recent weeks amid an unprecedented crackdown by federal immigration authorities.

The U.S. government maintained in new court filings that the Palestinian activist, 30, could be arrested because he was a “flight risk.”