California Code, Labor Code - LAB § 2806

(a) No employer, whether private or public, shall discontinue coverage for medical, surgical, or hospital benefits for employees unless the employer has notified and advised all covered employees in writing of any discontinuation of coverage, inclusive of nonrenewal and cancellation, but not inclusive of employment termination or cases in which substitute coverage has been provided, at least 15 days in advance of such discontinuation.

(b) If coverage is provided by a third party, failure of the employer to give the necessary notice shall not require the third party to continue the coverage beyond the date it would otherwise terminate.

(c) This section shall not apply to any employee welfare benefit plan that is subject to the Employee Retirement Income Security Act of 1974.