Cliff Sims, the former White House communications aide who wrote an insider account of life working for President Trump, is suing the president in his official capacity, alleging that he used his campaign organization as a “cutout” to improperly seek retribution against former employees and keep them from invoking their First Amendment rights.

Mr. Sims was a White House aide from the beginning of the administration. But it was the campaign organization that filed an arbitration claim against him last week, accusing him of violating the nondisclosure agreement he signed with it during the 2016 presidential race with the publication of his book, “Team of Vipers,” last month.

The White House had dozens of people sign such agreements at the beginning of the president’s term. But those agreements are widely seen as likely unenforceable. In the suit, Mr. Sims says he does not recall whether he signed one when he came to the White House.