China offers a masterclass in how to humble big tech, right?

ANTITRUST USED to be as American as apple pie. The Boston Tea Party was, in part, a protest against the monopoly of the British East India Company. The word itself stems from the trusts, such as Standard Oil, that lorded it over the American economy in the 19th century. For stretches of the 20th it became America’s charter not just for free enterprise, but for political freedom. Contrast this with China, a Communist dictatorship whose AntiMonopoly Law, introduced in 2008, has more often than not been used only to cudgel foreign firms. In such hands, it is easy to dismiss trustbusting as Orwellian gobbledygook.

And yet suddenly antitrust in China has come to life in the way police internal affairs have done thanks to the British cop show “Line of Duty”: as a source of unending fear and fascination, carried out by agencies with impenetrable acronyms and a keenness for Stasi-like dawn raids. In short order, it has transformed the country’s erstwhile tech giants into simpering poodles.

The onslaught marks the rise of a new sort of regulatory authoritarianism. Both America and China have similar qualms about the influence of their big technology firms. But since President Xi Jinping gave the nod to his trustbusting warriors last autumn, China has leapfrogged America in the speed, scope and severity of its antitrust efforts,...