“We note that if the book is distributed by you in Australia and our client is correct as to the defamatory imputations contained within the book, we are instructed to initiate immediate defamation proceedings against the Publisher, and our client will have no alternative but to join you as a party to those proceedings as a distributor,” the letter warned. The lawyers did not respond to a request for comment.

Howard, who is Australian and the former editor of The National Enquirer, features prominently in “Catch and Kill.” The book outlines his assistance to Weinstein, including an instance where he forwarded the producer “dirt” on the actor Rose McGowan after she tweeted about “my rapist.”

The Daily Beast, which earlier reported Howard’s threat, also wrote that Howard was taking similar legal action in Britain, Ireland and the United States, though the book was available for sale in those countries.

In a tweet on Tuesday, Farrow expressed his disappointment after an Australian reader noted her pre-ordered copy had “disappeared” from Amazon’s Kindle store, saying the book retailers had “caved and banned it due to frivolous legal threats.”