The Court of Appeal in Belfast has ordered the North's Department of Health to draw up guidelines on when an abortion may be performed, following a case brought by the fpa charity, formerly known as the Family Planning Association.
The fpa had appealed against a ruling made in July last year, when another judge rejected its argument that the North's abortion law was unclear and needed clarification.
The fpa's Northern Ireland director, Ms Audrey Simpson, who welcomed the ruling, said: "We work with women who have a crisis pregnancy, and it was very clear to us the medical profession and the women don't know when they can have a termination and when they can't."
The North was excluded from the 1967 Abortion Act, which made Britain the first country in the world to legalise abortion. Terminations are only allowed in cases where the mother's life is at risk or there is a serious danger to her mental or physical health.
The Irish Family Planning Association in Dublin yesterday welcomed the ruling and said it hoped it would end confusing and often inconsistent medical practice. Its chief executive, Mr Niall Behan, said: "For too long women in the North have been denied medical treatment to which they may be legally entitled, and this may be the first real step in rectifying this regrettable situation.
"Not until the Northern Ireland guidelines are clarified will we be able to comment on what this means for women in the Republic."
However, the Pro-Life Campaign said it hoped the ruling would not blur the distinction between necessary medical interventions in pregnancy and procedures which directly target the life of unborn children.
Dr Ruth Cullen, of the Pro-Life Campaign, said: "The Department of Health has a duty to ensure Northern Ireland's long-established ethos of care for both mother and baby is preserved and not subverted by those wishing to see abortion available on wide-ranging grounds."
Between 1,000 and 2,000 women are estimated to travel to Britain from the North each year to have abortions.
In yesterday's ruling Lord Justice Nicholson said doctors were not adequately aware of the principles governing the law in Northern Ireland, but the judgment should not be interpreted as a liberalisation of abortion rules.
Additional reporting by Reuters