In California there is no required reason for a divorce such as adultery. It is a "no fault" state. If you want to divorce your spouse on the grounds of "adultery" and want to subpoena the telephone records as part of the divorce proceedings to prove "adultery" once the dissolution proceeding has been filed, the attorney for the other side could most likely "block" the intended subpoena on the grounds of relevance to the divorce proceeding under California law by filing a motion with the court to stop the document production requested.The court will hear the motion and make a decision based upon the paperwork submitted.If you has a lawsuit against someone where private phone records are sought for some reason other than adultery purposes in California such as proving that someone was talking on the cell phone when the accident happened, you most likely would be entitled to those records.