These questions will be answered next month when a French court passes judgment on an attempt by the film star Alain Delon to block the writing of the first unauthorised account of his turbulent life.
The book does not, and may never, exist. Delon brought the case on the basis of an 18-page synopsis, which a French publisher sent to his lawyers. The author, Bernard Violet, is suing the publishers, Grasset, for breach of confidence.
The magazine Marianne has published extracts from Delon's formal complaint, including a precis of Mr Violet's synopsis. The book would, among other things, explore Delon's admitted friendships with criminal figures and contacts with the far right. In passing, the actor accused Mr Violet (a respected investigative author and journalist) of being a "pot-holer of dustbins and investigator of gutters". Mr Violet is cross-suing Delon for defamation.
From the Tribunal de Grande Instance next month, a changed, and chillier, legal landscape for all journalists and writers working in France may emerge. If Delon wins, it will be possible for public figures not only to stop publication of information but also, in effect, to prevent writers from gathering or checking such information.
Delon objects to the proposed book on two grounds: firstly, it infringes his right to privacy, guaranteed by French law; secondly, he says many of the allegations in the synopsis are inaccurate and defamatory. If he wins, Mr Violet would be unable to continue his work.
The author's lawyers argued during a court hearing this month that such a ban would amount to a serious restriction on the freedom of speech and liberty of the press (first declared in France in 1793). Journalists and authors must be accountable in law for what they have written, the lawyers said; but punishing them for what they might write would establish a new and dangerous principle and take France into the realms of Third World justice.
However, an interim ruling by the Tribunal de Grande Instance took Delon's side, fining Mr Violet pounds 3,000 for even considering writing the book and ordering him, in effect, to stop work on it.
What exactly is Delon afraid of? Although much of the synopsis has been published by Marianne, it is not possible for the Independent on Sunday to repeat the contents in detail without itself falling foul of French law. Suffice it to say that the proposed book would expand the existing evidence that Delon's success in portraying romantic tough-guys was rooted in personal observation.
Mr Violet says he wants to write a positive book about Delon, as one of the great French post-war film actors. But he also wants to explore his admitted friendships with criminal figures; his close relationship with a Yugoslav hoodlum, Stefan Markovic, whose still-unexplained murder in 1968 caused a political scandal in France; his declared admiration for and contacts with the French far right, including Jean-Marie Le Pen; and, in so far as French privacy laws permit, his energetic and unconventional love life.
"I believe that Delon is deliberately confusing the laws on privacy in France, which I respect, and have always obeyed, with the other laws on defamation and freedom of speech," Mr Violet said.
Under French law, it is illegal to write, even accurately, about the romantic and family life of a public figure without his or her permission. However, it is legal to write, accurately, about other activities, including open friendships, politics and business.
"The fact is that I have a right to write about his contacts with criminal figures, his political activities and his commercial activities," Mr Violet said. "Many of these things are already known about and admitted by him."
Mr Violet's previous works include a biography of Jacques Cousteau and an excellent account of the career of the international terrorist, Carlos the Jackal. Carlos is the only person to have previously sued the author; the terrorist lost.
As a result of the publicity over the Delon book, Carlo recently wrote to Mr Violet from prison to say he regretted having sued him, since his account of his career was "exceptionally rigorous and fair, for a book of its kind". "One could not have a better testimonial than that," said Mr Violet.