The Attorney General has said there are no grounds to appeal against the Old Bailey judgment that stopped the prosecution of a fugitive republican for the IRA's Hyde Park bombing.
Dominic Grieve told the Northern Ireland Affairs Committee at Westminster that the judge's reasoning in staying proceedings against John Downey was "powerful and persuasive", rendering the case effectively "unappealable".
The prosecution of Mr Downey (62), from Co Donegal, over the 1982 bomb was halted in February after Mr Justice Sweeney found he had been wrongly sent a Government letter of assurance in 2007 informing him the authorities were not pursing him, when in fact the Metropolitan Police were looking for him.
The judge decided his prosecution had therefore been an abuse of process. Mr Downey denied involvement in the attack in which four soldiers were killed.
Giving evidence to the committee's inquiry, Mr Grieve was asked on several times by MPs to justify the decision not to appeal against Mr Justice Sweeney's judgment.
"The judge's reasoning as set out in the final paragraphs of his conclusions seemed to me to be rather powerful and persuasive," explained the Attorney General.
"Now prosecutors shouldn't just go and appeal a decision unless they think they have good grounds for doing it.
"All I can say about that is we looked at it very carefully, and the independent view that had been formed by the CPS (Crown Prosecution Service), and indeed the view which I formed when I read it and which we then discussed, was that the judgment was unappealable."
Earlier former Attorney General Lord Goldsmith, who was in office when the scheme was set up and operated, conceded that public confidence in the rule of law could have been dented by the Downey case. But he insisted that one error should not undermine what was a well intentioned process.
"There was a bona fide intention to deal with a very difficult situation in order to advance the peace process in a way that didn't damage the justice system, which didn't involve removing people from prosecution in circumstances where prosecution was justified," he said.