Laws in the US are different from many other countries. If people like Preston don't like Italian laws, he should stay out of Italy. We know that novelist Doug Preston injected himself into an ongoing serial murder investigation in a foreign country because he wanted a juicy story to help his career. He slid up to an Italian journalist who had connections to police. The prosecutors office decided that Preston was interfering with the investigation, and indeed became suspicious of Preston's activities and knowledge of the investigation. As a result, Preston was detained and questioned for something like 5 hours. This so tremendously upset Preston that he left the country, and has not stopped talking about it since that event years ago.
Are we supposed to think that this now means that journalists are not at liberty to report facts and news in Italy? Of course not. Are we supposed to think that journalists can say whatever they want, true or false, about public figures? Again, of course not. I think it means that novelists should not interfere with a police investigation.
I'd like to know what Preston thought would happen when he injected himself into a murder investigation. Did he think that because he was a novelist, the police would take him into their fold and treat him like an investigator? Was he upset that he was considered to be interfering? What exactly is his complaint? I view him as a guy with an agenda who conveniently attached himself to Knox to further his cause - and career as a novelist.