Standing by President Trump’s side in Helsinki for their first bilateral summit, Russian President Vladimir Putin made what Trump described as an “incredible” offer: He would help U.S. investigators gain access to Russian intelligence officers indicted for the 2016 election hacking, on one small condition. “We would expect that the Americans would reciprocate and they would question [U.S.] officials … who have something to do with illegal actions on the territory of Russia,” Putin said, producing the name to indicate what actions he had in mind: “Mr. Browder.”

Bill Browder, an American-born financier, came to Russia in the 1990s. The grandson of a former general secretary of the Communist Party USA, Browder by his own admission wanted to become “the biggest capitalist in Russia.” He succeeded and was for a decade the country’s largest portfolio foreign investor.

Whatever the sins of Russia’s freewheeling capitalism, Browder’s real crime in the eyes of the Kremlin came later, after he had been expelled from Russia in 2005. In 2008, his Moscow lawyer, Sergei Magnitsky, uncovered a tax scam involving government officials that defrauded Russian taxpayers of $230 million. He did what any law-abiding citizen would, reporting the crime to the relevant authorities. In return, he was arrested and held in detention without trial for almost a year. He was beaten and died on Nov. 16, 2009, at Moscow’s Matrosskaya Tishina prison under mysterious circumstances. Officials involved in his case received awards and promotions. In a chilling act worthy of Kafka, the only trial held in the Magnitsky case was a posthumous sentencing of himself — the only trial against a dead man in the history of Russia.

It was then that Browder turned from investment to full-time advocacy, traveling the world to persuade one Western parliament after another to pass a measure that was as groundbreaking as it would appear obvious: a law, commemoratively named the Magnitsky Act, that bars individuals (from Russia and elsewhere) who are complicit in human rights abuses and corruption from traveling to the West, owning assets in the West and using the financial system of the West. Boris Nemtsov, then Russia’s opposition leader (who played a key role in convincing Congress to pass the law in 2012), called the Magnitsky Act “the most pro-Russian law in the history of any foreign Parliament.”

It was the smartest approach to sanctions. It avoided the mistake of targeting Russian citizens at large for the actions of a small corrupt clique in the Kremlin and placed responsibility directly where it is due. It was also the most effective approach. The people who are in charge of Russia today like to pose as patriots, but in reality, they care little about the country. They view it merely as a looting ground, where they can amass personal fortunes at the expense of Russian taxpayers and then transfer those fortunes to the West. In one of his anti-corruption reports, Nemtsov detailed the unexplained riches attained by Putin’s personal friends such as Gennady Timchenko, Yuri Kovalchuk and the Rotenberg brothers, noting that they are likely “no more that the nominal owners … and the real ultimate beneficiary is Putin himself.” Similar suspicions were voiced after the publication of the 2016 Panama Papers, which showed a $2 billion offshore trail leading to another close Putin friend, cellist Sergei Roldugin. Some of the funds in his accounts were linked with money from the tax fraud scheme uncovered by Magnitsky.

Volumes of research, hours of expert testimony and countless policy recommendations have been dedicated to finding effective Western approaches to Putin’s regime. The clearest and the most convincing answer was provided, time and again, by the Putin regime itself. It was the Magnitsky Act that Putin tasked his foreign ministry with trying to stop; it was the Magnitsky Act that was openly tied to the ban on child adoptions; it was the Magnitsky Act that was the subject of the 2016 Trump Tower meeting attended by a Kremlin-linked lawyer; it is advocating for the Magnitsky Act that may soon land any Russian citizen in prison. It was the Magnitsky Act that Putin named as the biggest threat to his regime as he stood by Trump’s side in Helsinki.

After the Trump-Putin meeting, the Russian Prosecutor-General’s Office released the names of U.S. citizens it wants to question as supposed associates of Browder. The list leaves no doubt as to the nature of the “crime.” It includes Michael McFaul, senior director for Russia policy at the Obama White House and later U.S. Ambassador in Moscow who oversaw the “compiling of memos to the State Department … on the investigation in the Magnitsky case.” It includes David Kramer, former assistant secretary of state in the George W. Bush administration, who, as president of Freedom House between 2010 and 2014, was one of the most effective advocates for the Magnitsky Act. Perhaps most tellingly, it includes Kyle Parker, now chief of staff at the Commission on Security and Cooperation in Europe, who, as the lead Russia staffer at the commission, wrote the bill that subsequently became the Magnitsky Act.

Vladimir Putin has left no doubt: The biggest threat to his regime is the Magnitsky Act, which stops its beneficiaries from doing what has long become their raison d’être — stealing in Russia and spending in the West. It is time for more Western nations to adopt this law — and for the six countries that already have it to implement it with vigor and resolve.