The Supreme Court has begun hearing an appeal into a High Court judgment that Dunnes Stores had breached European regulations by replicating a woman's top and shirt designed by UK company Karen Millen.
The case relates to a woman's black knit top and a blue striped shirt and a brown striped shirt, the designs of which were not registered.
In December 2007, the High Court ruled that Dunnes Stores had infringed Karen Millen's rights to unregistered designs under a 2002 EU regulation.
It was the first time the EU regulation was contested in Ireland.
Michael Cush, Senior Counsel for Dunnes Stores, said copying is standard in the industry of unregistered designs.
The only issue, he said, was that of unregistered rights. He said a community unregistered design should not be upheld unless it is new and has individual character.
Mr Cush said the High Court had taken a very narrow approach and interpretation of unregistered designs.
He said the test as to whether unregistered rights had been breached should not have been confined to a comparison against just one item.
The shirts were produced in 2005 and sold in Ireland and England of that year.
Dunnes Stores sold similar garments under the Savida Label in 2006.