In hypermodern Hong Kong, a debate over 17th-century fashion is dividing the city's legal circles.

The city's lawyers are among the last in the world to wear judicial wigs, those curly, horsehair headpieces that are a legacy of more than 150 years of British colonial rule. The affection is so great that one group of lawyers that doesn't wear wigs wants the right to don them. The city's wig-wearers are resisting.

The...