Sens. John McCain (R-AZ) and Ben Cardin (D-MD), former US Attorney for the Southern District of New York Preet Bharara, and former US Ambassador to Russia Michael McFaul are angry with the Trump administration’s Department of Homeland Security for revoking the visa of British hedge fund manager William Browder, an outspoken critic of Russian President Vladimir Putin.

Browder’s visa was revoked on Saturday, the same day Putin managed to get Browder placed on Interpol’s international watch list. Being on the list means he can’t leave the UK without potentially facing arrest.

Though far from a household name, Browder is no random billionaire. He’s spent most of the past decade pursuing anti-Putin legislation from country to country in the name of one of his former employees, Sergei Magnitsky, who died under horrific circumstances in a Russian prison nine years ago.

In this country, Browder’s lobbying efforts led Congress to pass the Magnitsky Rule of Law Accountability Act in late 2012, a bill that singled out a number of Putin allies and denied them US visas. The Kremlin has been trying to get him put on an Interpol watch list ever since; this week, after four earlier efforts, it finally succeeded.

In an email exchange with Vox, Browder said he believed the timing of the Russian move was no coincidence. Canada just passed a law closely modeled on the Magnitsky Act that sanctions foreign officials “responsible for, or complicit in, extrajudicial killings, torture or other gross violations of internationally recognized human rights.”

Browder said he doesn’t expect the US visa restriction to hold beyond this week.

“The Canadians passed the Magnitsky Act last week which infuriated Putin,” Browder wrote me late Monday afternoon. “He gave a speech on Thursday night attacking Canada and me personally. He also instructed his prosecutor to add me to the Interpol list. That coincided exactly with my US ESTA (my visa waiver document) being revoked and losing my Global Entry status.”

The visa denial may have been triggered automatically by Browder’s inclusion on the Interpol list, but it sparked furious detractions from across the political spectrum.

Bill Browder is a champion of anti-corruption in #Russia. DHS must immediately review decision to revoke his visa. https://t.co/j0Pzt8t9QH — John McCain (@SenJohnMcCain) October 23, 2017

.@BillBrowder has been a global advocate for anti-corruption in #Russia. @DHSgov should immediately review the decision to revoke his visa. pic.twitter.com/dwKGh3pm0s — Senator Ben Cardin (@SenatorCardin) October 23, 2017

Browder is the activist Putin loves to hate

Sergei Magnitsky was a 35-year-old Russian lawyer employed by Hermitage Capital, the hedge fund Browder created. In 2007, Magnitsky uncovered a $230 million tax fraud scheme that implicated top Kremlin officials and friends of Putin.

Magnitsky was arrested in November 2008 and died a year later, still in prison. The official cause of death was untreated pancreatitis, a severe abdominal inflammation, and heart failure, but many outside observers say he’d been beaten and tortured while in police custody.

Browder soon began speaking out in Washington about the young lawyer’s death. After intense lobbying, in late 2012 the House and Senate overwhelmingly approved the Magnitsky Act. (The Obama administration initially opposed the bill because they thought it might hamper their efforts to improve the broader US relationship with Putin.)

The legislation froze the assets of those suspected of being involved in Magnitsky’s death and denied them US visas. That list first named 18 Russian officials. It has since grown to 44, including names of others suspected of human rights abuses.

Upon its passage, Russian Foreign Minister Sergei Lavrov promised retaliation. “We will also close entry to Americans who are guilty of human rights violations," he said.

Putin was furious, and the Russians retaliated by stopping all US adoptions of Russian children.

That’s why when Donald Trump Jr.’s now-infamous meeting with a Kremlin-backed lawyer first came to light in July, the younger Trump insisted that the real reason for the meeting was an innocuous one: to discuss the adoption of Russian children. That conversation is seen by many as a means of talking about the sanctions, not the children.

Last week, when Canada passed its own version of the Magnitsky Act, the Russians issued an ominous statement.

“The latest decision by the Parliament of Canada guised as a pro-human rights and anti-corruption measure is a deplorably confrontational act blatantly interfering into Russia’s domestic affairs,” an official Russian Federation Embassy posting read. “This hostile move, as well as any new anti-Russian sanctions, will be met with resolve and reciprocal countermeasures.”

Those first moves appear to target Browder himself.