The story behind Donald Trump Jr.'s controversial meeting with a Russian lawyer during the 2016 presidential campaign has turned out to be a complicated one linking adoptions, sanctions, and frozen assets.

President Donald Trump's son had initially said the discussion was set up to talk about adoptions, but he later admitted that he had attended in the hopes of learning potentially damaging information about Hillary Clinton.

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But many believe some Russians ultimately saw the meeting as an opportunity to advocate for U.S. lawmakers to repeal a controversial law that penalizes many Russians. Bill Browder repeated that claim during testimony to Senate lawmakers in a recent hearing.

"It's clear the interest and goal in that meeting was to repeal the Magnitsky Act. It's the one thing we can agree with certainty that happened in that meeting," Browder said.

Learn more about the Trump-Russia saga:

14 PHOTOS Putting the Trump-Russia timeline into perspective See Gallery Putting the Trump-Russia timeline into perspective June 7: The 2016 primary season essentially concludes, with both Donald Trump and Hillary Clinton as the presumptive party nominees June 9: Donald Trump Jr. — along with Jared Kushner and former campaign chair Paul Manafort — meets with Kremlin-connected lawyer Natalia Veselnitskaya. June 9: Trump Trump tweets about Clinton's missing 33,000 emails July 18: , on the first day of the GOP convention, that the Trump campaign changed the Republican platform to ensure that it didn't call for giving weapons to Ukraine to fight Russian and rebel forces Washington Post reports , on the first day of the GOP convention, that the Trump campaign changed the Republican platform to ensure that it didn't call for giving weapons to Ukraine to fight Russian and rebel forces July 21: GOP convention concludes with Trump giving his speech accepting the Republican nomination July 22: WikiLeaks releases stolen emails from the Democratic National Committee July 25: Democratic convention begins July 27: In final news conference of his 2016 campaign, Trump asks Russia: "If you're listening, I hope you're able to find the 30,000 emails that are missing" August 4: Obama CIA Director John Brennan confronts his Russian counterpart about Russia's interference. "[I] told him if you go down this road, it's going to have serious consequences, not only for the bilateral relationship, but for our ability to work with Russia on any issue, because it is an assault on our democracy," Brennan said on Obama CIA Director John Brennan confronts his Russian counterpart about Russia's interference. "[I] told him if you go down this road, it's going to have serious consequences, not only for the bilateral relationship, but for our ability to work with Russia on any issue, because it is an assault on our democracy," Brennan said on "Meet the Press" yesterday October 4: WikiLeaks' Julian Assange WikiLeaks' Julian Assange says his organization will publish emails related to the 2016 campaign October 7: WikiLeaks begins releasing Clinton Campaign Chair John Podesta's emails October 7: Department of Homeland Security and the Director of National Department of Homeland Security and the Director of National Intelligence release a statement directly saying that Russia is interfering in the 2016 election October 31: "This WikiLeaks is like a treasure trove," Trump says on the campaign trail November 4: "Boy, I love reading those WikiLeaks," Trump says from Ohio. Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

Browder played a key role in getting the 2012 law was passed, which was named in honor of Sergei Magnitsky, a Russian lawyer Browder hired who was jailed and ultimately died in Russian captivity after working tirelessly to uncover a $230 million tax fraud scheme.

Browder was an American born to a Russian family who was the biggest investor in the Russian stock market at one point. But that all changed in 2005 he says after he became an outspoken critic of corporate governance in the country, alienating Vladimir Putin and others.

Lawmakers passed the Magnitsky Act in order to punish various businessmen and officials believed to be connected to Magnitsky's death, freezing Russian assets and barring suspected human rights abusers from entering the United States.

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Russia quickly retaliated by passing a law that prohibits Americans from adopting Russian children, a popular phenomenon in the years leading up to the law. The two issues have been linked ever since.

"Russian adoptions was really code for Russian sanctions," Browder claims.

Russian adoptions have come up since. When news of a second quiet Trump-Putin meeting emerged earlier this month, Trump insisted that the two only shared "pleasantries" and discussed adoption.

Since then, Browder has claimed that Putin and his associates have spent millions of dollars -- including hiring the Russian lawyer Natalia Veselnitskaya -- to try and get the act repealed.

Browder speculates that it is an effort to protect human rights abusers as well as free up frozen assets including money belonging to Putin himself.

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