Rubio’s letter notified DHS that he had revoked both targets’ visas, setting in motion plans for U.S. Immigration and Customs Enforcement to arrest and attempt to deport them, according to a senior DHS official and another U.S. official who spoke on condition of anonymity to describe how the operation against Khalil took shape.

Nearly 100 people were arrested after protesters gathered at Trump Tower in Manhattan Thursday to demand the release of Mahmoud Khalil, a Palestinian activist and Columbia University alumnus who was detained by immigration authorities on Saturday.

The current administration wants to go after protesters using an obscure Cold War-era statute.