Between classes, when throngs of students stream into and out of Columbia University ’s campus, the security lines can back up like a TSA checkpoint. There’s a switch-back path of metal fencing that leads into a white tent, where two sets of guards check and then swipe campus ID cards before letting students in and out.

Nationwide protests are planned this weekend after Mahmoud Khalil, a former Columbia University student activist, was arrested by immigration authorities, fueling tensions between the Trump administration and student movements over immigration policy.