The Supreme Court has found the government has used public money on the Children's Referendum campaign in a manner that was not fair, equal or impartial.
Its decision overturns last week's High Court ruling against challenger Mark McCrystal.
The Court's finding said that it does not consider it either appropriate or necessary to grant an injunction, as it is to be assumed that the respondents will cease distributing and publishing the material.
In 1995 the Supreme Court held in the McKenna case that public funding should not be used in a Referendum to espouse a particular point of view.
Mark McCrystal, an engineer from Kilbarrack, alleged that is exactly what the Government was doing, claiming it was promoting a Yes vote in its information campaign for the upcoming Children's Referendum.
The High Court disagreed and found the content on the campaign website, booklet and in its advertising was neutral.
That has been unanimously overturned by a five-judge Supreme Court following an urgent hearing this week.
In a preliminary judgment, it has concluded there are extensive passages in the booklet and on the website which do not conform to the McKenna principles.
The website for the referendum has been taken down.
The children's referendum.ie address is not currently directing users to the site and it is not known if or when it will be back up.