In A v Governor of Arbour Hill Prison [2006] IESC 45; [2006] 4 IR 88; [2006] 2 ILRM 481, the Supreme Court of Ireland ruled that a finding that criminal legislation is unconstitutional need not render existing convictions void.

[2] Subsequently, in CC v Ireland,[3] the Supreme Court found that that section was inconsistent with the constitutional rights of the accused since it failed to afford the accused the opportunity to defend a statutory rape charge by pleading that he made a reasonable mistake as to the age of the girl.

Before the Supreme Court, A argued that the retrospective effect of a finding of unconstitutionality is essentially unqualified.

[5] Conviction of unlawful carnal knowledge of an underage girl has always been condemned in the State and has been an offence since the time the legislation was formed.

Pending cases are also included in this but a final judicial decision is excluded from retrospective effect.

Public policy reasons require that there be a limit on retroactive effect of judicial decisions.

Also without such limitation, allowing every previous decision to be set aside would be a great injustice to all the victims and against the fundamentals of society.

[5] A declaration of invalidity should not be applied to all existing previous decisions as this would be disadvantageous to an ordered society, victims of those cases and a coherent legal system.

There can be exceptional situations where an accused argues that such a decision have denied him justice and thus should be deemed as void.