CA Penal Code Section 1237.5

No appeal shall be taken by the defendant from a judgment of conviction upon a plea of guilty or nolo contendere, or a revocation of probation following an admission of violation, except where both of the following are met:

(a)

The defendant has filed with the trial court a written statement, executed under oath or penalty of perjury showing reasonable constitutional, jurisdictional, or other grounds going to the legality of the proceedings.

(b)

The trial court has executed and filed a certificate of probable cause for such appeal with the clerk of the court.