The State has dropped a possession charge of €2.5m worth of ecstasy following a Court of Appeal ruling that some drugs had been unconstitutionally banned.
It brings to three the number of such charges which have been struck out.
There are fears that dozens of more possession charges will have to be dropped because of the successful challenge to the Misuse of Drugs Act 1977.
The accused man, who was also found with a similar amount of cannabis, had pleaded guilty to possessing more than 250,000 ecstasy tablets for sale or supply in 2013.
However, counsel for the Director of Public Prosecutions (DPP), Tony McGillicuddy BL, asked the court to withdraw the ecstasy charge and proceed solely on the cannabis counts in light of the ruling.
Gary Byrne (42) of Belcamp Gardens, Coolock, Dublin, also pleaded guilty to possession of a total of €2.52m worth of cannabis resin and cannabis herb at Rosemount Business Park in Ballycoolin and North West Business Centre in Blanchardstown in June 2013.
The man will be sentenced on Thursday by Judge Patricia Ryan at Dublin Circuit Criminal Court.
The drugs concerned are now illegal again after emergency legislation was rushed through the Government.
The Government was forced to act after a decision by the Court of Appeal on a challenge to the Misuse of Drugs Act 1977.
The case was brought by a man prosecuted for possession of methylethcathinone in 2012.
He denied criminal charges of supplying the substance and argued the regulations were unconstitutional.
The three-judge court unanimously agreed a regulation making the possession of methylethcathinone illegal was invalid, as it was unconstitutional.
Because of the way the laws are drawn up, the ruling had the knock-on effect of temporarily legalising the possession of other drugs in the same category.
Dozens of drug-related convictions are expected to be open to challenge after the ruling.
Only cases currently in progress may be overturned, with the ruling not affecting convictions which were already handed out. Yesterday's case was the third such charge to be dropped since the ruling.
Last Thursday, charges were withdrawn against a man caught with over €17,000 worth of ecstasy. Darren Snee (25), of Oak Court Close, Palmerstown, Dublin, pleaded guilty to possession of the drug for sale or supply hours before the appeal court issued its judgment.
Mr Snee still faces sentencing later this month for possession for sale or supply of cannabis worth €819 and cocaine valued at €399, both of which were unaffected by the ruling.
Mr Snee pleaded guilty at Dublin Circuit Criminal Court to possession of cocaine, cannabis and MDMA, otherwise known as ecstasy, for sale or supply at his home on November 18, 2013.
Earlier last week, the State also withdrew charges against a man accused of holding a small amount of ecstasy.
The man still faces sentencing for possession of €23,000 worth of heroin, which he claimed he was holding to clear a €30,000 debt.
Phillip Farrell (35) of Cushlawn Park, Tallaght, Dublin, was caught storing the drugs at his home on two separate occasions.
He pleaded guilty at Dublin Circuit Criminal Court to possession of heroin for sale or supply on December 3, 2013 and February 2, 2014.
He also admitted to possession of cannabis resin with a market value of €732 for supply on December 3, 2013.
John Byrne BL, prosecuting, told the court that on foot of the Court of Appeal ruling, the State was withdrawing two charges relating to unlawful possession of a quantity of ecstasy. This amount had an estimated market value of just over €200.