The phrase "black robes" refers to the long, dark-colored robes typically worn by judges or other legal professionals in a court of law. Full definition
He's a big presence on - screen so naturally the main in black robes gets his own character vignette. (thehdroom.com)
Judges of the German Federal Courts wear purple robes with red lining, while judges of the Federal Patent Court wear black robes with blue vests. (jjmccullough.com)
Middle - level judges wear black robes with color lining, or a sash on the front. (jjmccullough.com)