Business and Professions Code section 480 prohibited the denial of a professional license solely on the basis of a felony or misdemeanor conviction once there was a certificate of rehabilitation for a felony or the applicant fulfilled conditions siimilar to that of a certificate of rehabilitation on a misdemeanor. (See Bus. Prof. Code section 480 (b).)

In essence, the board could deny, suspend, or revoke a license because of a conviction of a crime that is substantially related to the qualifications, functions, or duties of the business or profession but it could not deny a license solely on that conviction if the above applied.  So, a certificate of rehabilitation would protect an applicant or licensee, but a dismisal (often referred to as an expungment) pursuant to Penal Code 1203.4 would not.

As of January 1, 2015, subdivision (c) has been added that prohibits denial of a professional license solely on the basis of a conviction that has been dismissed pursuant to Penal Code sections 1203.4, 1203.4a, or 1203.41.

There is a long list of boards covered including the Medical Board of California, the Bureau of Real Estate, Board of Registered Nursing, the Dental Board of California, the Board of Behavioral Sciences and many others.  See Business and Professions Code section 101 for a complete list.