He’s not some clerk, he’s a judge whose rulings included classified cases. Judges are sworn and this is what they declare when they are nominated:
I solemnly swear, as a judge of a common court, to serve the Republic of Poland faithfully, to uphold the law, to perform the duties of a judge conscientiously, to administer justice in accordance with the law, impartially according to my conscience, to observe state and official secrecy, and in my actions to be guided by the principles of dignity and honesty.