Both California and federal law require 60 days notice for mass layoffs. The CA WARN Act has more protections for workers than the federal WARN Act, i.e., it also applies to part-time workers.

In California, it is illegal to require a terminated employee to sign an NDA to receive severance paid to waive the required WARN notice. A company attempting to enforce such an NDA would key face judicial sanction in court (including paying the former employee's legal fees) and likely pay fines to the CA Labor Dept as well.