On campuses from New England to Southern California, students leading one of the largest protest movements in decades have increasingly strapped on face masks and checkered Palestinian kaffiyehs in a polarizing bid to protect their anonymity even as they demand universities and governments be held to account. ...

The presence of large groups of masked demonstrators also appears to be contributing to a growing sense of unease at schools like Columbia and the University of California, Los Angeles, which overnight on Tuesday looked more like conflict zones than institutions in the middle of final exams.

Frustrated provosts and deans worry that the regular masking is making it easier for outsiders to infiltrate their campuses, a charge Columbia cited late Tuesday to justify mass arrests of demonstrators who had occupied Hamilton Hall on its Upper Manhattan campus.