A law that says no-one can be fined or jailed for a drug-related offence has been struck down in the High Court.
A High Court judge struck down a law that was made under the former government to ban the selling of drugs in the city.
Lawyers for the law, which was introduced in the late 1990s, argued it would create a criminal offence and be discriminatory.
The High Court in Dublin rejected that argument.
The law, called the Narcotics Control Strategy, or NCS, has been in effect since October 2015.
The Irish Times understands that the law was struck down by the High Council for Justice, Equality and Justice in the Northern Ireland Assembly (ICJ).
It was also struck down earlier this year by the Supreme Court in the Republic of Ireland.
The Supreme Court ruling came in relation to the Criminal Assets Bureau, which is run by the Irish Revenue.
The ICJ case concerned the application of a new law that has been made under former Taoiseach Enda Kenny to bar people from selling drugs in certain areas of Dublin.
The ruling, by Justice Michael Hogan, said it was a “treaty” and was an attempt to impose “a criminal offence” on those who were not members of the criminal justice system.
Justice Hogan said that under the law the person in question could not be fined for the possession of drugs if it was part of a group, a person working in a shop or a person who was a dealer.
The judge said that it was an “undue interference” with the “rights of others” and that the “law is a violation of the fundamental rights of those it is designed to protect.”
The law has been used by both the DUP and Sinn Féin.
However, the DUP said that the government had used the law to “sink” people who have been jailed for drug-driving offences.
“The DUP is disappointed with today’s judgment and is concerned by the implications of today’s decision,” a spokesperson for the party said.
“Sinn Féen supports the principle of decriminalisation and believes the decriminalisation of drug-taking is a good first step towards reducing drug-impaired driving and reducing public health and social harm.”
The DUP also claimed that the ban on selling drugs would lead to a “dramatic drop in the number of people being sent to jail”.
The ruling has not been made public.