The U.S. immigration authorities who arrested pro-Palestinian activist Mahmoud Khalil in New York on March 8 did not have an arrest warrant, according to information from a legal file cited Friday by the American news outlet Axios.

Lawyers for these Department of Homeland Security (DHS) agents argued, according to this file, that they were not required to have a judicial warrant before detaining Khalil, the Columbia student. "The agents faced urgent circumstances justifying a warrantless arrest; it's common and usual for DHS to completely process a person's case once they are in custody," the lawyers wrote in the document initially filed with an immigration court on Wednesday, then submitted to a federal court on Thursday.

The lawyers claimed that the agents had reasons to believe that Khalil "would escape before they could obtain the warrant" when they approached him in the lobby of his building in New York. This warrant was eventually received after the detention of the Syrian-born activist, who holds a green card, and his transportation to an Immigration and Customs Enforcement (ICE) office.

Khalil was among the leaders of the pro-Palestinian protests at Columbia University in recent months. His arrest sparked a wave of indignation across the United States, notably among freedom of expression advocates.

Khalil's lawyer, Marc Van Der Hout, claimed that the agents had informed his client that they possessed a warrant during his arrest and that it was recorded in the arrest report.

"The government's admission is astounding, and it's absolutely outrageous that they attempted to claim before the immigration judge – and the world – in their first arrest report submission that a warrant existed when it did not," Van Der Hout stated in a statement, according to which this situation "should, in accordance with the law, lead to the end of the proceedings" against Mahmoud Khalil.