Eamonn Harrison, from Northern Ireland, who is wanted in connection with the discovery of 39 bodies in a refrigerated shipping container in Essex, has been granted permission by a High Court judge in Dublin to appeal against his extradition to the UK.
Mr Justice Donald Binchy accepted arguments raised by Harrison's defence team related to the issuing of the European Arrest Warrant.
His lawyers claimed there were "manifest errors" in the original warrant.
They contended that when additional information was sought from the UK authorities that that information was provided by the Crown Prosecution Service, instead of a judicial authority.
Judge Binchy said there was a need to explore the points raised in a higher court.
He formally made an order granting extradition to the UK, but placed a stay on the execution of that order pending the outcome of the Court of Appeal proceedings.
Ten teenagers, including two 15-year-old boys, were among eight women and 31 males, all Vietnamese nationals, whose bodies were discovered in the trailer in an industrial park in Grays in the early hours of October 23.
On Tuesday it was revealed the provisional cause of death for those in the lorry was a combination of suffocation and overheating in an enclosed space, Essex Police said.
A team of detectives investigating the deaths are in Vietnam to meet the victims' families.
Lorry driver Maurice Robinson has previously admitted conspiracy to assist unlawful immigration and acquiring criminal property - namely cash.
The 25-year-old, of Laurel Drive in Craigavon, Northern Ireland, has yet to enter pleas to 39 counts of manslaughter, conspiracy to commit human trafficking and transferring criminal property.
Co-defendant Christopher Kennedy, 23, from Darkley, County Armagh, Northern Ireland, has denied being involved in the alleged human trafficking plot and denied conspiring to assist unlawful immigration.
A further hearing will take place on March 16 at the Old Bailey, with a provisional trial set for October 5.
A 22-year-old man was arrested in Northern Ireland on Sunday on suspicion of manslaughter and facilitating unlawful immigration. He is currently in custody in Essex, the force said.
Gheorghe Nica, 43, of Basildon, was arrested at Frankfurt Airport on January 29 under a European Arrest Warrant and will appear at the Old Bailey on March 16, Essex Police said.
He faces 39 counts of manslaughter and one count of conspiracy to assist unlawful immigration.
Eamonn Harrison, 23, of Mayobridge, Co Down, Northern Ireland, is wanted in the UK on 39 charges of manslaughter and charges of conspiracy to traffic people and conspiracy to assist unlawful immigration.