Hello shein,
A criminal judge, Jewish or otherwise, in the U.S. court system can impose a penalty under U.S. law on a defendant, Jewish or otherwise, who has been found guilty whether or not that particular penalty is also warranted under halacha. It is the U.S. judge’s legal right, job, and duty to impose this penalty when a defendant properly under the court’s jurisdiction is before the court for sentencing, after that defendant was tried according to the laws of the land for a crime recognized by the criminal code in the relevant jurisdiction.
As an attorney here in the U.S., I can only speak for how things work here. What country do you live in, or what country are you talking about, when you say that the judge has no right to penalize a Jew with a penalty unwarranted under Halacha?