But by the end of 2019, key players at the Treasury, including Ms. Mandelker, had started to leave the Trump administration, and State Department officials like Mr. Pham said they found it more difficult to get new Magnitsky sanctions imposed.
The officials turned to the Senate Foreign Relations Committee for help in keeping up the pressure on Mr. Gertler. In August, members of the committee sent the Treasury Department a bipartisan letter that did not mention him by name but carried a clear message.
To help build democracy and fight corruption in Congo, the letter said, the United States “should designate additional officials and companies responsible for or complicit in high-level corruption, including the misappropriation of state assets, for targeted financial and travel sanctions.”
But Mr. Gertler’s team, including Mr. Dershowitz and Mr. Freeh, had a different message. They had solicited a letter from Ms. Frazer attesting to Mr. Gertler’s role in the peace negotiations nearly two decades earlier and distributed it to Trump administration officials. As far back as 2019, they set up meetings with State Department officials, making the case that his activities had helped the interests of the United States.
“His first effort was a lobbying effort,” Mr. Shaviv said of Mr. Gertler’s campaign.
But Treasury rules state that “professional services such as lobbying, public relations, government affairs, consulting and business development are not legal services, and are generally not covered” by an exemption that allows people under sanctions to hire lawyers.
Mr. Dershowitz said the meetings were permitted because he did not lobby the White House or others on this matter.