"法官的职权" can be translated into English as "the powers and duties of a judge" or more concisely as "a judge's authority" or "judicial authority of a judge".
"The powers and duties of a judge" explicitly mentions both the authority and responsibilities of a judge.
"A judge's authority" emphasizes the power or jurisdiction a judge holds.
"Judicial authority of a judge" also conveys the legal power or right a judge has to make decisions and enforce the law.
Choose the expression that best fits the context in which you intend to use it.