Last December the ruling Liberal Democratic Party rammed one of the most controversial bills in Japan’s postwar history through the Diet, or parliament, with an uncharacteristic lack of debate. The “Protection of Specially Designated Secrets Act” passed even as opposition politicians knocked over desks, chairs, and one another while trying to reach the podium to block it. Outside, nearly 10,000 protesters formed a human chain around the government building and chanted, “No Return to Fascism!”

The new law is stunningly broad. As an editorial in the leading Yomiuri newspaper noted, “The policy establishes a National Security Council for military matters and also creates comprehensive controls on foreign relations, the economy, and technological development.” At stake are central tenets of Japan’s democracy—the right to know, the right to a free press, the right to privacy—all of which the wide-ranging, ill-defined law imperils.

The law is also unpopular. By the end of December, 80 percent of the public called for revisiting or scrapping the law entirely. Sharp criticism continues to appear regularly in every form of media and from a wide variety of individuals and organizations, including Japan’s numerous press associations, the Japan Bar Association, and the Japan Medical Association. The latter is deeply alarmed by a provision in the law that requires doctors to divulge patient information, including about mental health. But the draconian legislation will go into effect this coming December, if its opponents are not able to stop it.

Why was the law enacted? In large part, it was an effort to please the United States—Japan’s most important ally. For decades, Washington’s key Japan handlers—“the Alliance managers”—have urged Japan to institute something like our NSC or NSA to control information inside the country and coordinate security between the two nations....