Mr. Trump’s inauguration in January 2017 was a high point for Mr. Barrack: The inaugural committee he led set records for the amount of money raised and spent to celebrate an inauguration.
But critics claimed the inaugural became a hub for peddling access to foreign officials and business leaders, or people acting on their behalf. The United States attorney’s office in Manhattan opened an investigation into possible violations of campaign finance law, focusing partly on whether foreigners, who were barred from contributing to the $107 million inaugural fund, illegally funneled donations through Americans.
Questions about whether Mr. Barrack complied with the Foreign Agents Registration Act, commonly known as FARA, arose during the Russia inquiry led by the special counsel, Robert S. Mueller III, and were referred to the United States attorney’s office in Brooklyn.
Three of the six former Trump aides who were charged by the special counsel acknowledged violating the foreign lobbying statute in their guilty pleas: Mr. Manafort, Rick Gates, who served as deputy campaign chairman for Mr. Trump in 2016, and Michael T. Flynn, Mr. Trump’s former national security adviser.
But while the Justice Department has been trying for several years to step up criminal enforcement of FARA requirements, such cases are typically difficult to prove. Whether someone is acting at the behest of a foreign official “is a very hard thing to investigate or to decide,” Adam S. Hickey, the deputy assistant attorney general in charge of the national security division, said in a recent interview.
Central to the inquiry into Mr. Barrack are his dealings with Mr. al-Malik, who is well connected in the court of Crown Prince Mohammed bin Zayed, the de facto ruler of the United Arab Emirates widely known by his initials, M.B.Z., and is close to the prince’s brother, Sheikh Hamdan bin Zayed, who oversees the United Arab Emirates’ intelligence services. Sheikh Hamdan is considered to be Mr. al-Malik’s patron and a major financier of his business activities.
When Mr. Trump was elected, Mr. al-Malik received a coveted invitation to the inaugural’s most exclusive event — the chairman’s dinner, hosted by Mr. Barrack.