A Taiwanese appeals court has thrown out a drug-driving ruling because police never explained why they pulled the driver over — a win for the driver, and a warning to police about sloppy traffic stops.

• A man in Chiayi was caught driving during a two-year license suspension for drunk driving, with ketamine in his system.
• Authorities fined him heavily, revoked his license, and seized his plates for two years.
• He argued that traces of a drug in urine do not prove he was unfit to drive, and that the stop itself was illegal.
• The Kaohsiung high administrative court found the first ruling never showed what legal grounds police had to stop him at all.
• The case goes back to the lower court for a fresh hearing.

Outlook: The lower court will have to prove the traffic stop was lawful before any penalty can stand, a test that could reshape how police justify roadside checks.