Legal Question in Criminal Law in California

You mean you wanted a trial before a judge without a jury and your lawyer wouldn't go along? This violates common sense on your part. Having a "judge alone," if you mean what I think you mean, is what lawyers call a "slow guilty plea."

Possibly the DA did not agree to a bench trial. VERY UNUSUAL, but their right to do so.

Another way to read your question is that you have a co-defendant and asked to be tried separately. If that is what happened, then I would need to know more about your case before I could say whether there is anything wrong with the decision at all, let alone what requirements it violated.