Mr. Gertler was found to have used his friendship with Mr. Kabila to act as a middleman for mining sales in Congo, requiring other companies to go through Mr. Gertler to do business with the Congolese state, costing the country more than $1.36 billion in revenue, the Treasury Department said in 2017.
“Gertler is an international businessman and billionaire who has amassed his fortune through hundreds of millions of dollars’ worth of opaque and corrupt mining and oil deals in the Democratic Republic of the Congo,” the Treasury Department said in 2018, as it expanded the sanctions against him.
The application to issue a new license that allows United States companies to do business with Mr. Gertler was handled by the law firm Arnold & Porter. Baruch Weiss, a lawyer at the firm who handled the matter, declined to comment Sunday, as did Mr. Dershowitz.
Mr. Gertler as of October 2018 had hired Mr. Dershowitz and Mr. Freeh, as well as Gregory A. Paw, a former federal prosecutor, to work on the matter, with the team then targeting the Treasury and State Departments to try to get the changes made, lobbying disclosure reports show. Also registered to lobby on the matter is Gary Apfel, a lawyer who like Mr. Dershowitz was involved in several successful pardon appeals to Mr. Trump in recent months.
Erich C. Ferrari, a lawyer who represents U.S. and foreign companies on sanctions issues, reviewed the license that the Treasury issued on Jan. 15 and said he was surprised at how broadly it appeared to allow United States companies to work with Mr. Gertler, despite the sanctions in 2017 and 2018.
“As hard as it is for me to believe that a license this broad was issued and exists, I have to say that it is indeed a license authorizing Gertler and companies owned 50 percent or more, directly or indirectly, to engage in business with and through U.S. banks,” Mr. Ferrari said.
The Sentry recommended in a statement Sunday that the United States banks not unblock Mr. Gertler’s money or “open accounts or otherwise conduct transactions for or on behalf of Gertler and his network until this matter is fully investigated and resolved.”
Kenneth P. Vogel contributed reporting.