I was recently denied benefits for STD and would like to know what my rights are with regards to the appeal in the state of CA (i.e. laws)?

Insurance companies constantly attempt to cut off benefits of people on short term and long term disability, as doing so saves them huge dollars. (In fairness, insurance companies also know that some folks would just as soon collect disability forever rather than return to work, and feign or exaggerate symptoms, to claim disabilities that do not exist, and actually are working while on disability.)

One way the insurance companies cut off claimants is by selecting "friendly" Independent Medical Examiner to review case files and conduct the exams. They keep careful data on which IMEs tend to find there is or is not a disability, and the selection process they use is far from random. (On the other side, some claimants/plaintiffs lawyers do the reverse.)

Appealing from a denial of disability benefits is often a rather complicated process. If the employer is large enough to be covered by ERISA there are very strict time lines that must be adhered to, with internal appeals followed by the right to sue in court. 

That's not always easy, and most people need insurance lawyers to successfully handle these cases; most take the cases on a contingency basis, and under some circumstances the legal fees are paid for the insurance company wrongfully denying the benefits. 

AttorneyPages.com lists some of the very best insurance lawyers in California.