President Obama's visit to Vietnam highlights ever-growing ties between former Cold War adversaries. Obama announced Monday in Hanoi that Washington would be fully lifting a long-standing U.S. embargo on lethal arms sales to Vietnam, a move seen as a bid to hedge against Chinese expansionism in the region.

As my colleague David Nakamura reports from Vietnam, Obama hailed "a new moment" in U.S.-Vietnamese relations and hoped that the latest move "removes a lingering vestige of the Cold War."

But critics and rights groups point to the enduring authoritarian practices of Vietnam's one-party government.

“Even as it faces the glare of global attention with the US President’s visit, the Vietnamese authorities, shamefully, are carrying out their repressive business as usual,” Rafendi Djamin, Amnesty International’s director for Southeast Asia and the Pacific, said in an emailed statement to journalists.

Most recently, the government cracked down on a series of protests this month prompted by an ecological disaster that affected the country's fisheries. In April, local residents and fishermen in a number of Vietnam's central provinces reported the mass death of fish along vast stretches of the coast. Tons of dead fish and other seafood had washed up on beaches.

“If you sail just three miles offshore, you can see dead fish all over the ocean floor,” a state-run newspaper quoted a fishermen as saying.

It's not clear what caused the deaths, but many, including state media, pointed the finger at industrial plants dumping toxic waste into the ocean. Angry protests followed in Hanoi and Ho Chi Minh City over lax standards and oversight, especially with facilities run by influential foreign conglomerates.

“The impact is severe, both physically and morally,” Le Dang Doanh, an economist and former government adviser, told the Wall Street Journal. “Trust has been reduced to the lowest level.”

As in China, another Communist-run state, environmental activism is one of the few outlets of public dissent and civil society mobilization that can function in Vietnam without being immediately quashed. The country has seen protests, big and small, on issues such as China's maritime drilling for hydrocarbons along endangered reefs or even the planned removal of trees in Hanoi's public spaces.

Even then, the authorities are wary of allowing these passions to be unleashed. As the dead fish protest movement took off, uniformed and plainclothes police were soon stationed outside the homes of activists and human rights defenders, according to Amnesty International.

Some demonstrators were attacked and intimidated, while others have been arrested, Amnesty said. The international rights group detailed more in its statement:

Among those who have been swept up by the most recent wave of arrests which took place in the last week is Nancy Nguyễn, a US citizen, who arrived in the country on May 17, 2016 to join the protests. Two days later, she reported on social media that 20 security officials were outside her hotel.
Nancy Nguyễn has not been heard from since and her current fate and whereabouts remain unknown.
Nguyễn Viết Dũng was arrested on May 20 in Hồ Chí Minh City, having travelled there from his home town in Nghệ An province. He was released on May 23 after being flown back to Nghệ An.
He was only recently released in April 2016, after a one-year jail term for participating in a peaceful protest in Hanoi.
Journalist Phạm Đoan Trang and blogger Vũ Huy Hoàng were arrested in Hanoi on the morning of May 23. The details of their arrests are unclear.
On the morning of May 23, Nguyễn Ngọc Như Quỳnh and Nguyễn Bá Vinh were arrested in Nha Trang. Nguyễn Bá Vinh had travelled to a local beach in the early morning with a banner which read “Why have the fish died?”
He was physically attacked by a group of men in plain clothes. Nguyễn Ngọc Như Quỳnh went to the beach to help him and was also attacked. The two were arrested at around 8am local time and detained until 4pm.
None of the men involved in attacking them were arrested. This is second time in a week that Nguyễn Ngọc Như Quỳnh has been arrested. On May 15, she was detained in Hồ Chí Minh City while attempting to join demonstrations in the city.

Of course, while Washington pays lip service to the importance of human rights and freedom of expression in societies elsewhere, such an agenda is almost always outweighed by strategic considerations.

"The United States government has been telling the Vietnam government for years that they need to show progress on their human rights record if they are going to be rewarded with closer military and economic ties," said John Sifton, Asia policy director for Human Rights Watch, as cited by The Washington Post's Nakamura. "Yet today President Obama rewarded Vietnam even though its government has done little to earn it: It has not repealed any repressive laws, nor released any significant number of political prisoners, nor made any substantial pledges."