Kevin McAleenan, named the acting head of the U.S. Department of Homeland Security after the abrupt resignation of Kirstjen Nielsen on Sunday, has long-ago Big Law ties and one of his former law school classmates is a U.S. Justice Department lawyer who blessed the Trump administration’s first travel ban.

McAleenan is succeeding Nielsen at the helm of Homeland Security, serving as the acting secretary amid substantial turmoil over immigration policies. Nielsen, who met with Trump on Sunday, reportedly did not resign willingly. It’s unclear how long McAleenan will serve as the temporary leader.