Publicly elected officials have a higher bar to meet because, unlike private citizens, statements made about them are probably a matter of public importance.
Over the weekend, Trump said "libel laws are very weak in this country" and that "if they were strong", the book wouldn't have been published in the first place.
"I'm going to open up our libel laws so when they write purposely negative and awful and false articles, we can sue them and win lots of money", he said on the campaign trail in February 2016.
The White House and Trump have denounced Wolff and his work, which also included accusations made by the president's former chief political strategist, Steve Bannon, about Donald Trump Jr.'s infamous meeting with Russians in June 2016. "You wouldn't have things like that happen where you can say whatever comes to your head".
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Trump's attorney, Charles Harder, sent a cease and desist letter to Wolff and his publisher, Henry Holt & Co., threatening legal action if they moved forward with the publication of the book.
No lawsuit has been filed.
If you've been paying attention to the politics and policies of President Trump at least over the last two years, you'll notice something very unusual has been happening, particularly this week.
Trump has floated changes to libel statutes in response to negative media coverage in the past, saying in October that it's "disgusting the press is able to write whatever it wants to write".
Meanwhile, the president also addressed his latest call with South Korean President Moon Jae-In, who Mr. Trump says, was thankful for the role the US played in the talks between North Korea and South Korea this week over the North's participation in the Winter Olympics. It held that a publisher would be guilty of defamation or libel if he/she knew the challenged statement was false or acted with reckless disregard of its truth or falsity.