The High Court has ruled against a 58-year-old Wicklow woman who took a landmark case challenging the law on assisted suicide.

Marie Fleming, who has multiple sclerosis, wanted an order declaring a section of the law that bans assisted suicide declared invalid under the Constitution and incompatible with the European Convention on Human Rights.

However, the High Court said while her right to autonomy was affected by the ban, it could not agree the legislation was disproportionate.

The three-judge divisional High Court gave its judgment today after a six-day hearing last month.

The judges described Ms Fleming as one of the most remarkable witnesses it ever had the privilege to encounter. 

High Court President Nicolas Kearns described her courage in adversity as "both humbling and inspiring".

The court agreed personal autonomy, especially in medical matters, was a core Constitutional value affected by a ban on assisted suicide, but it could not agree the ban was a disproportionate interference with this right.

The three judges agreed a competent adult had the right to refuse medical treatment even if it led to death, but the taking of active steps by a third party to bring about the death of another is entirely a different matter, the court ruled.

If the court could tailor-make a solution that would affect Ms Fleming only without implications for third parties there might be a good deal to be said for her case.

However, the court could not be so satisfied.

There was ample evidence to demonstrate that a relaxation of the ban would be impossible to tailor to individual cases and would be inimical to the public interest in protecting the most vulnerable in society.

The court also ruled it would be unconstitutional for the DPP to issue guidelines on prosecutions for assisted suicide, but the court "felt sure" the director "in this of all cases" would exercise her discretion in a humane and sensitive fashion.

Where there was evidence of compliance with a list of factors, such as those specified in the UK, presented to the DPP after an assisted suicide, the DPP remained free to exercise her discretion and make a fully informed decision on whether or not to initiate a prosecution.

The approach means the law would remain intact while ensuring the DPP is given the fullest opportunity to consider special factors in this case, the judgment said.

Ms Fleming was awarded the costs of this case as it was deemed to be of exceptional public importance.

In December, Ms Fleming told the court the ban on assisted suicide was forcing her to live against her will in a life of pain and indignity.

The former lecturer is almost completely physically incapable and would need help to take her own life.

She argued the law discriminates against her by banning assisted suicide while an able-bodied person is free to take their own life.

Her lawyers said this impaired her rights to privacy, autonomy and dignity provided by the Constitution and the European Convention on Human Rights.

But lawyers for the State argued that while it was not a criminal act, there was no constitutional right to take your own life.

The State was entitled to maintain the ban, as a matter of social policy to protect others.

Doctors who gave evidence for the State said they believed the removal of the ban would be the slippery slope towards involuntary euthanasia.

Ms Fleming's solicitor Bernadette Parte said she is disappointed and saddened by the ruling.

They are considering an appeal, but have to study the judgment first.