The ban on gay men giving blood in Northern Ireland is irrational, a High Court judge has ruled.
Mr Justice Treacy also held that Health Minister Edwin Poots breached the ministerial code by failing to take the issue before the Stormont Executive.
His verdict in a challenge brought by an unidentified homosexual man represents a major victory for campaigners seeking equal status with the rest of the UK.
The complete prohibition, put in place during the 1980s Aids epidemic, was lifted in England, Scotland and Wales in November 2011.
It was replaced by new rules which allow blood from men whose last sexual contact with another man was more than a year ago.
The 12-month deferral was left in place following a Government Advisory Committee report. It identified a much shorter window period during which infection with blood-borne viruses could not be detected.
Mr Poots maintained the ban in Northern Ireland on the basis of ensuring public safety.
But a gay man, granted anonymity because of his perceived vulnerability, launched a judicial review challenge to Mr Poots' position.
Mr Justice Treacy heard claims that the minister displayed apparent bias which went beyond religious beliefs and into the realms of prejudice.
Attorney General John Larkin questioned the legitimacy of the challenge.
However, Mr Justice Treacy said the decision was made against the Secretary of State's recommendation that the report from the advisory committee on the Safety of Blood, Tissues and Organs should be followed.
He said: "The minister has decided that MSM (males who have sex with other males) behaviour creates such a high risk of infection to the donor that such donors must be permanently deferred with the result that such blood cannot enter the Northern Ireland blood stock.
"Importing blood from other places which do accept MSM donors, even in limited quantities, leaves the door open for MSM blood to do just that.
"There is clearly a defect in reason here."
He added: "As such the minister had no authority to act without bringing them to the attention of the Executive Committee which he failed to do."