The High Court has refused a second attempt by French authorities to have Ian Bailey extradited to face trial over the death of Sophie Toscan du Plantier.
Mr Justice Tony Hunt said the second application for his extradition was an abuse of process and the matter had already been decided by the Supreme Court in 2012.
The judge said the fact that the domestic legal system had comprehensively determined the issue was ignored in processing the latest application.
French prosecutors want Mr Bailey to go on trial for the murder of the French filmmaker, who was found beaten to death outside her holiday home in Schull, west Cork in December 1996.
Mr Bailey was twice arrested and questioned in connection with her death but prosecutors said there was no evidence to charge him.
He has always denied any involvement in her death and has alleged a garda conspiracy to frame him for her killing.
French authorities previously sought the surrender of Mr Bailey in 2010 but this application was refused by the Supreme Court in 2012.
A second extradition request was issued last year.
In his ruling this morning Mr Justice Hunt said the issue had already been decided by the Supreme Court and the High Court was bound by that.
He also concluded that the proceedings were an abuse of process.
In his judgment this morning, Mr Justice Hunt said the parties in the case had received a "binding and conclusive decision of the Supreme Court".
He said 21 years had passed since the crime in question was committed and seven years since the first extradition warrant issued.
Over four years passed since the date of the Supreme Court ruling to the issue of a new warrant.
"Apparently neither the minister nor the requesting authorities considered it appropriate to furnish any information by way of explanation for the elapse of this period of time," the judge said.
He added that the period of delay had not been explained adequately or at all.
He said there had been no engagement by the minister or the requesting authorities with the unusual fact in an extradition case that the matter had been comprehensively and repeatedly investigated by authorities here.
He said the Director of Public Prosecutions had concluded long ago that there is no basis for either charge or trial and a comprehensive statement of reasons for this decision had come into the public domain during the Supreme Court proceedings.
This application did not engage with this situation at all, the judge said.
He said proceedings were issued for the surrender of a person entitled to the protection of our laws and Constitution for trial and possible imprisonment for 30 years.
He said the new request ignored the fact that the domestic legal process had comprehensively determined that the allegation could not even give rise to a charge let alone a trial and this "highly unusual" state of affairs contributed to his finding of abuse of process in this case.
Lawyers for Minister for Justice Charlie Flanagan were not present in court for the judgment.
The case will return to court next week for any applications by the State on residual legal issues which may have to be determined.
Speaking outside court, Mr Bailey said he was pleased and delighted with the judgment.
But he said it was not the end of the matter as he said the State would almost certainly appeal.
But, he said, life goes on.
He said it was noticeable that the State, which had taken the case against him, and which he said had put him through a form of torture for 20 years, on and off, was not even represented in court for the decision. He said that was "astonishing".
Mr Bailey said he was very, very sympathetic to the family, who believed that he had something to do with the death of their daughter.
But he said he had nothing to do with it.
He said it would be good if a new piece of evidence came to light or someone admitted the truth but he said he did not suppose that was going to happen.
The Court of Appeal is due to give its decision in Mr Bailey's appeal against the failure of his civil case against the State and gardaí on Wednesday.
