Kilkenny County Council has been ordered to halt the construction of two new bridges over claims the work is causing very severe and possibly irreversible environmental damage.
The order was secured by local student and campaigner Christopher O'Keeffe, from Freshford Road and will remain in force until next Wednesday.
O'Keeffe claims Kilkenny County Council has breached planning consents while constructing Green's Bridge and a footbridge about a mile downstream on the River Nore.
The court heard the river is a special area of conservation and the only habitat in the world where you will find the hard water pearl mussel.
Ms Justice Marie Baker has agreed to put a temporary stop to both construction projects on environmental grounds.
She said she was particularly impressed by the evidence of an ecologist that this was the most serious incident of environmental pollution that she had ever seen in an area of conservation.
The local authority has not had its say yet, but it will be put on notice of the order and have a right of reply when the case returns to court next week.