Dean Jennifer Mnookin announced the policy in a lengthy letter to the faculty, students, and staff. Here's the key point:
Given the current situation surrounding the COVID-19 pandemic, especially here in Southern California, I have made the decision, with the approval of our Executive Vice Chancellor and Provost, that our fall semester’s courses at the law school, with very limited exceptions possible for a small number of live-client experiential classes, will be entirely remote. ...
It's worth reading the whole thing.