Denise Brewster, 42, a lifeguard from Coleraine, Northern Ireland, challenged a ruling that a nomination form had to be completed before she could receive payments under the public sector scheme.
She was told she would not be automatically entitled to a “survivor’s pension” as she would have been if she and her partner for ten years, Lenny McMullan, had been married.
But five Supreme Court justices yesterday unanimously ruled the nomination requirement must be “disapplied” and declared Ms Brewster was entitled to receive payments.
Later there was disagreement in the legal world over whether the impact of the ruling would be confined to Northern Ireland or would have much wider significance.
Ms Brewster’s solicitor, Gareth Mitchell of public law firm Deighton Pierce Glynn, said the ruling could affect millions of cohabitees across the UK.
He said: “Denying bereaved cohabitees access to survivor pensions causes huge distress and financial hardship.”
Mr Mitchell said that, following the 2012 High Court ruling in the Brewster case, local government pensions schemes in England, Wales and Scotland removed the nomination form requirement, although this was not retrospective.
But other legal experts say the court’s reasoning was limited to the facts of Ms Brewster’s case, involving the Northern Ireland Local Government Officers’ Superannuation Committee (Nilgosc), and the wider impact will be limited.
Other public sector pensions schemes that require nomination forms would only be ruled unlawful if the providers cannot provide evidence justifying different treatment for unmarried couples, lawyers suggested.
Ms Brewster and Mr McMullan lived together for ten years and got engaged on Christmas Eve 2009, but he died suddenly between Christmas night and the early hours of Boxing Day.
He had 15 years’ service with Translink, which delivers Northern Ireland’s public transport services, and had been paying into Northern Ireland’s local government pension scheme.