Portugal’s Supreme Court ruled Kate and Gerry McCann cannot sue the former Portuguese detective who published the book for libel.
In 2015, a Lisbon court ordered Goncalo Amaral to pay Kate and Gerry McCann €500,000 (£429,000) in compensation for the allegations made in his book, Maddie: The Truth of the Lie.
The book was published in 2008, three days after Portuguese authorities formally closed their inquiry and cleared the McCanns of any wrongdoing.
Mr Amaral argued in his defence that the claims in his book stemmed from the police investigation.
He also noted Portuguese media had already reported the possibility the parents may have played a role in Madeleine’s disappearance.
More than £50,000 was raised in support for the detective, donated via a Go Fund Me page, after he was ordered to pay damages.
The McCanns had sought €1.2m (£1m).
However, an appeals court overturned the conviction last year before reaching Portugal's top court.
Madeleine disappeared from a holiday home in Portugal's Algarve region in May 2007, days before her fourth birthday.
British police are still investigating her disappearance.