The High Court will decide tomorrow whether work can continue on the final section of the M50 motorway at Carrickmines in south Co Dublin.
The work has been delayed by almost two years due to legal challenges concerning the remains of a medieval castle which lie in the path of the motorway.
New legislation was signed into law last month allowing the roadway to go ahead despite the presence of the monument, and Dún Laoghaire-Rathdown County Council resumed work yesterday.
However, campaigners say the High Court should have been notified before the work started. And they claim the new legislation is unconstitutional.
They are seeking an injunction stopping the work as soon as possible. They received permission today to have a hearing of their case at 2pm tomorrow afternoon. The work will continue in the meantime.
The court was told that the motorway is almost complete on either side of Carrickmines Castle.
