So what? A judge has the authority to prohibit anything that he or she feels is prejudicial to either of the two parties there.
So, my argument is that a judge's authority is neither absolute, nor all encompassing.
The judge is not even the real judge of the case, the Jurors are, it is they who decide guilt and innocence — in American jurisprudence the judge is, at best, a referee, he is absolutely not supposed to be a black robed god-king.