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The Justice Department sued a onetime close friend and aide to the first lady, Melania Trump, on Tuesday to try to recoup the profits from a tell-all book that disclosed embarrassing details about her, the third lawsuit in recent months where the department has taken on a White House antagonist.

The decision to file the lawsuit raised new questions about whether President Donald Trump is using the powers of the Justice Department to settle personal scores that have little to do with the federal government.

The aide, Stephanie Winston Wolkoff, wrote in her book, “Melania and Me: The Rise and Fall of My Friendship With the First Lady,” that Melania Trump was selfish and image-obsessed, had a strained relationship with her stepdaughter Ivanka Trump and was largely unfazed by her husband’s insults and lewd comments about women.

The Justice Department alleged in the suit that Winston Wolkoff violated a nondisclosure agreement she had signed with the government when she agreed to volunteer to help Melania Trump in the early months of the administration. The pact forbade her from disclosing confidential details she learned during her time working for the first lady, the lawsuit said.

“Defendant Wolkoff has been, and will continue in the future to be, unjustly enriched in the amount of profits, advances, royalties and other advantages resulting from publicity given to the unauthorized disclosures contained in her book,” according to the suit.

The lawsuit takes a broad view of the government’s powers over the rights of former employees. Although it is routine for national security officials to sign agreements not to disclose classified information, Winston Wolkoff had no access to such material and the private conversations and internal deliberations she described were akin to the kinds of accounts that former aides in many White Houses go on to disclose in memoirs.

The Justice Department said the administration had standing to bring the suit. “This was a contract with the United States and therefore enforceable by the United States,” said Kerri Kupec, a department spokeswoman.

A lawyer for Winston Wolkoff said in a statement that “this lawsuit is entirely meritless.”

“It represents an effort by the Trumps to enlist the DOJ to pursue entirely personal goals and interests,” said the lawyer, Lorin Reisner. “The position staked out in the lawsuit also violates the First Amendment.”