The Justice Department sued Stephen Wynn, the former casino mogul, on Tuesday, seeking to force him to register as an agent of the Chinese government and saying he had made requests on the government's behalf to Donald J. Trump when he was president.

According to the lawsuit, Mr. Wynn passed along a request to Mr. Trump from the Chinese government to kick a Chinese national out of the United States.

The Justice Department said that Mr. Wynn was a foreign agent because he was a middleman for the Chinese government. The department asked Mr. Wynn to register himself as a foreign agent in three years, but he refused.

The department's commitment to ensuring transparency in our democratic system is demonstrated by the first affirmative civil lawsuit under FARA in more than three decades.