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.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.

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.

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.

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.