The University of California, Berkeley, has opened a Title IX civil rights investigation into whether a law professor harassed a Muslim student during a dinner last month in the professor’s backyard.

The investigation by the university’s Office for the Prevention of Harassment and Discrimination stems from an April 9 incident at the home of professor Catherine Fisk and her husband, who is dean of the university’s law school.

Graduating law student Malak Afaneh said she was subjected to…