ARGENTINES hoping to preserve their 30-year-old democracy had reason to cheer this week when midterm congressional elections resulted in a decisive defeat for President Cristina Fernández de Kirchner. The president’s party lost in 12 of 23 provinces, including the capital and Buenos Aires province, which contain more than a third of the population. The vote virtually ensured that Ms. Fernández, who is in uncertain health following brain surgery, will not be able to change the constitution and run for a third term in 2015, and it gave a boost to a couple of moderate rivals who oppose her authoritarian populism.

Sadly, however, Ms. Fernández and her cronies still pose a threat to the country’s democratic institutions. That became clear Tuesday, when the Argentine Supreme Court, under heavy pressure from the president’s office, upheld a law aimed at destroying one of South America’s most important media firms, Grupo Clarín. The company operates one of Argentina’s biggest newspapers, called Clarín, which has been one of the few media outlets to challenge Ms. Fernández’s policies. The law would force the company to auction off cable television and Internet businesses that provide most of its revenue, thus reducing potential funding for Clarín’s newsroom.

Government officials have claimed that the law, which a lower court declared unconstitutional, is meant to prevent media monopolies and inject more diversity into news coverage and public debate. That doesn’t explain why other private media companies with multiple properties were exempted from the law, or the trumped-up criminal charges that were brought against Clarín’s owners, or the government’s seizure of the only newsprint producer or its ruthless campaign to starve Clarín and two other newspapers of advertising.

For years, Ms. Fernández and her late husband, who preceded her as president, have worked to concentrate power in their own hands. Major private companies, including the largest airline and oil company, were nationalized, along with private pension funds; according to the Inter American Press Association, 80 percent of media now parrot the government line. The membership of the Supreme Court was doctored in an attempt to stack it with a government majority. After it nevertheless struck down a government attempt to neuter the judiciary this year, it came under heavy pressure to approve the media law. The newspaper La Nación reported that Ms. Fernández and her legal adviser privately lobbied the chief judge and another justice.

The wave of authoritarian populism that swept across Latin America a decade ago is receding, and Argentines who hope to undo the damage done by the Kirchners have reason for hope. They could use help, however, from the hemisphere’s democracies, including the three that along with Argentina are members of the Group of 20. The United States, Brazil and Mexico should be asking whether a nation in the Western Hemisphere that stifles freedom of expression deserves to have its voice amplified through invitations to elite summit meetings. The obvious answer is no.