The Stormont Executive has failed in its legal duty to adopt an Irish language strategy, a High Court judge ruled on Friday.
Mr Justice Maguire held the administration to be in breach of a requirement imposed under decade-old legislation.
The challenge was mounted by Irish language group Conradh na Gaeilge.
The body issued judicial review proceedings over a failure to comply with a St Andrews Agreement pledge.
Mr Justice Maguire said: "It cannot have been the intention of Parliament that, after nearly 10 years from the coming into force of the Act in 2007, this obligation would remain unfulfilled."
Counsel for Conradh na Gaeilge contended that the failure to take any further steps contravenes the 1998 Northern Ireland Act.
The court also heard that the government is committed to implementing a European Charter for Regional or Minority Languages.
A barrister representing the Northern Ireland Executive countered that there had been "no inertia" on the issue.
He rejected any suggestion of a "sham process" and maintained that the draft strategy was properly assessed.
Dr Niall Comer, President of Conradh na Gaeilge, welcomed the judgement.
"Instead of implementing their commitments over the last 10 years, certain parties have opposed a development strategy for the Irish-language," said Dr Comer.
"The law has confirmed today, however, that there must be an end to the delay and to the pretence."