The High Court held that copper in the Cadia Mine is a "privately owned material" for the purposes of the Mining Act and as a result, the State of New South Wales must repay to Cadia seven-eighths of the royalties that have been paid since 1998 - an amount in excess of $10 million and more over the remaining 20 years of the life of the mine.

The case was decided with regard to the Cases of Mines (1568), which held that the Crown had the prerogative right to mines of gold and silver and other metals, including copper, with which gold or silver was mixed.

In the appeal to the High Court, the State of NSW claimed that the copper from the Cadia mine was vested in the Crown pursuant to its prerogative right to mines of gold and was therefore a publicly owned mineral, based on the argument that although the mines contained copper, they were characterised as mines of gold.