Justice Hugh Geoghegan: If every past conviction and sentence were declared a nullity because an offence was found to be unconstitutional, it would be contrary to any good order in a civilised society, Mr Justice Hugh Geoghegan said.
Allowing the appeal, he said criminal or court cases that had been concluded could not normally be reopened even if subsequently found to be unconstitutional. He accepted there may possibly be exceptions to a case being reopened, but in general it could not be done.
Nor, he said, was there any precedent for a collateral change of this kind.
"I am also firmly of the opinion that if the law were otherwise there would be a grave danger that judges considering the constitutionality or otherwise of enactments would be consciously or unconsciously affected by the consequences, something which in the view of Mr Justice Walsh, and endorsed by Chief Justice O'Higgins, should not happen," he said.
"I believe that on any reasonable interpretation of Bunreacht na hÉireann, convictions and sentences pursuant to enactments not declared unconstitutional, are at the very least deemed to be lawful at the time of the relevant court orders and must be treated as remaining lawful following on a declaration of unconstitutionality," he said.
He said the respondent pleaded guilty to a count of unlawful carnal knowledge with a girl under 15 and was sentenced to three years' imprisonment under section 1(1) of the Criminal Law (Amendment) Act 1935.
In the High Court, the respondent claimed that as a consequence of the declaration of unconstitutionality, he had pleaded guilty to an offence that did not exist and therefore his detention was unlawful.
Mr Justice Geoghegan said the judge upheld the submission but in his view it was incorrect.
"It is a fallacy to assume that once it is declared that a pre-1937 statutory provision creating an offence is inconsistent with the Constitution and was, therefore, not carried over, prior court orders made pursuant to proceedings under it must be treated as nullities," he said.
He quoted a previous ruling in a case concerning back tax which stated: "The correct rule must be that laws should be observed until they are struck down as unconstitutional."
Mr Justice Geoghegan said: "In this connection, I see no difference between post-1937 legislation and pre-1937 legislation. A judge bound under his declaration on taking office to uphold the laws would not be entitled of his own volition to disregard a pre-1937 statute on the basis of his or her own theory that the enactment was inconsistent with the Constitution.
"Unless and until there is a formal declaration to that effect, those laws are binding. They are binding because they must be deemed to be valid and constitutional."
Thus in the case of a prosecution under section 1(1) of the Criminal Law (Amendment) Act 1935, instituted and completed before any declaration of inconsistency was made by the court, an interpretation of the Constitution must clearly require that orders and warrants made in a completed criminal case under the impugned provision must continue to be deemed valid.
In interpreting a provision of the Constitution, it was always necessary to have regard to the general intent of the Constitution as a whole.