AS CHINA’S power grows, Vietnam has been working hard to build closer relations with the United States. Vietnam’spresident visited the White House in July; it has encouraged U.S. involvement in territorial disputes between China and several Asian countries, including Vietnam; and it is proposing to join the Trans-Pacific Partnership (TPP), a free-trade deal with the United States and 11 other countries.

The Obama administration has encouraged this shift as part of its “pivot” to Asia, which is intended to balance China’s influence. But, unlike most of its neighbors, Vietnam is doing little to distinguish itself from the Communist regime in Beijing. Like China, it has opened its economy to foreign investment and free markets. But, just as China’s new leadership has clamped down on dissent in the last year, so, too, has Vietnam’s. This year, at least 46 activists have been jailed for criticizing the ruling Communist Party or campaigning for human rights, according to the Wall Street Journal.

The regime’s latest victim was one of the country’s most popular and courageous advocates of greater freedom: Le Quoc Quan, a 42-year-old lawyer, outspoken Catholic and blogger. On Wednesday Mr. Quan was sentenced to 30 months in prison on trumped-up charges of tax evasion. He was arrested last December, a few days after publishing an article that questioned whether the Communist Party’s monopoly on power should be excised from the country’s constitution.

This is not the first time Mr. Quan has suffered repression. In 2007, he was arrested shortly after returning from a fellowship with the National Endowment for Democracy in Washington; he was released three months later after protests from Washington. In 2011, he was detained again for observing the trial of another dissident. In 2012, he was attacked and badly beaten by men he said were state security agents. In the face of all this, Mr. Quan persevered, posting on his blog regular accounts of human rights abuses and proposals for political liberalization.

A poem he wrote in prison while awaiting trial, posted online by Human Rights Watch , includes this stanza:

Suffering in every way is our miserable people

Achieved independence, yet no freedom

Widespread is the nation’s disease of corruption

No more rights of freedom and democracy

In dark cells, those who fight for it are imprisoned

Though Mr. Quan has long been a friend of the United States, the Obama administration’s reaction to his conviction was characteristically low-key. A statement issued by the U.S. embassy in Hanoi said “the use of tax laws by Vietnamese authorities to imprison government critics for peacefully expressing their political views is disturbing,” noting that it placed Vietnam at odds with the International Covenant on Civil and Political Rights. Should it not also place Vietnam outside the boundaries of a free-trade alliance that will depend on respect for the rule of law? Senior U.S. officials will be seeing their Vietnamese counterparts at an Asian summit meeting next week: That question should be on the table.