A US judge on Wednesday extended his order blocking federal authorities from deporting a detained Columbia University student, in a case that has become a flashpoint of the Trump administration's pledge to deport some pro-Palestinian college activists.

US District Judge Jesse Furman had temporarily blocked Mahmoud Khalil's deportation earlier this week, and extended the prohibition on Wednesday in a written order following a hearing in Manhattan federal court to allow himself more time to consider whether the arrest was unconstitutional.

The Department of Homeland Security says Khalil is subject to deportation under a legal provision holding that migrants whose presence in the country are deemed by the US Secretary of State to be incompatible with foreign policy may be removed.

"The Secretary of State has determined that your presence or activities in the United States would have serious adverse foreign policy consequences for the United States," read the DHS document, dated March 9, ordering Khalil to appear before an immigration judge on March 27.

The document did not provide additional detail.

The DHS did not immediately responded to requests for comment from reporters.

Khalil's lawyers say his arrest on Saturday by DHS agents outside his university residence in Manhattan was in retaliation for his outspoken advocacy against Israel's assault on Gaza following Hamas' October 2023 attack, and thus violated Khalil's right to free speech under the US Constitution's First Amendment.

"Mr. Khalil was identified, targeted, detained and is being processed for deportation on account of his advocacy for Palestinian rights," Khalil's lawyer Ramzi Kassem said in court. (Reuters)