HONG KONG — This city has long prided herself on respecting the rule of law — the ultimate guarantee of Hong Kongers’ freedoms, human rights and way of life. It is one of the attributes that make Hong Kong stand apart from cities on the Chinese mainland. Our practice of common law, together with an independent judiciary served by high-caliber judges, has earned us the trust and the confidence of friends and trading partners all over the world. Our legal system’s predictability and its freedom from political interference guarantee that no one will fall victim to the arbitrary exercise of power by government authorities.

Or so it did. All of this changed last Friday when Carrie Lam, Hong Kong’s besieged chief executive, unilaterally decided to invoke the Emergency Regulations Ordinance to prohibit face masks and other coverings at public gatherings. The new regulation — formally called the Prohibition on Face Covering Regulation and, more commonly, the face-mask ban — makes it a criminal offense punishable by one year of imprisonment for people to hide their faces in ways that prevent identification, even if they are participating in lawful meetings or marches.

Mrs. Lam said the ban was designed to stop violence and restore order, but her move only added fuel to the fire . Thousands of people — in masks — took to the streets all weekend, even after service was suspended across the entire underground system. There were clashes with police. A 14-year-old was shot in the leg.

The ordinance is an archaic statute from 1922, when Hong Kong was a British colony and the acts of the city’s governor were regulated by the monarchy in Britain. Since Hong Kong reverted to Chinese sovereignty in 1997, it has had its own Constitution, the Basic Law, which is supposed to protect the city’s autonomy from China under the “ One Country, Two Systems” principle . Acts of the chief executive should be reviewed for compliance with the Basic Law.