His attorney, Sergei L. Magnitsky, whom he tasked with investigating that theft, was thrown in jail in 2008 and died after being held for 358 days. An independent human-rights commission found that Magnitsky had been illegally arrested and beaten; the Kremlin maintains that he died of a heart attack. In 2012, as a direct result of a lobbying campaign by Browder, Congress passed the Magnitsky Act, which authorizes the president to deny visas to, and freeze the assets of, Russians believed to have been complicit in Magnitsky's death.

Browder began lobbying for tougher sanctions on Russia nearly a decade ago, following Magnitsky’s death. Browder says Magnitsky uncovered the $230 million stolen tax rebate, which implicated high-level Kremlin officials.

Putin’s decision to identify Browder on the world stage, standing next to the president of the United States at the end of a high-stakes summit, was either highly strategic or a crack in his ordinarily impenetrable facade. It reinforced Browder’s status as one of Putin’s top irritants, and it provided more evidence that a meeting at Trump Tower between Trump-campaign officials and a Russian lawyer—a key event in Mueller’s Russia probe—was blessed by the Kremlin.

The first sign that the Kremlin played a role in the Trump Tower meeting came last year, when it was revealed that a memo about Browder provided to the Trump campaign by the Russian lawyer Natalia Veselnitskaya mirrored a memo that had been given to Republican Congressman Dana Rohrabacher by Russia’s chief federal prosecutor, Yury Chaika, months earlier. Both memos accused Browder of renouncing his U.S. citizenship in 1998 for “tax reasons,” and alleged that Browder’s “illegal” schemes had cost Russia more than $16 billion in “unpaid taxes.”

The Trump Tower meeting itself was originally pitched to Donald Trump Jr. as an opportunity for “the crown prosecutor of Russia,” later identified as Chaika, to provide the campaign “with some official documents and information that would incriminate Hillary and her dealings with Russia.” The memo Veselnitskaya gave to Trump Jr. accused Browder of funneling money to Clinton via the principals of Ziff Brothers Investments, purportedly Browder’s biggest investors.

Fast-forward to Monday’s press conference, where Putin brought up all of the above in an apparent attempt to undermine Browder’s credibility in the most highly visible forum he could ever hope for. “Business associates of Mr. Browder have earned over $1.5 billion in Russia,” Putin said. “They never paid any taxes, neither in Russia nor in the United States, and yet the money escaped the country. They were transferred to the United States. They sent huge amount of money, $400 million, as a contribution to the campaign of Hillary Clinton … We have a solid reason to believe that some intelligence officers accompanied and guided these transactions. So we have an interest of questioning them.”