The federal government has argued that a court judgment over a mining lease would create "vast" claims for compensation from native title holders across the Northern Territory, if allowed to stand.
Commonwealth solicitor-general Stephen Donaghue KC told the full bench of the High Court sitting in Darwin that the government would be exposed to "a vast amount of compensation" if the appeal failed.
"The Commonwealth would be liable to pay compensation (to native title holders) with interest ... possibly over 100 years or more," Dr Donaghue said at the opening of the appeal.
In May 2023, a decision by the full bench of the Federal Court paved the way for the Gumatj to potentially receive up to $700 million compensation for bauxite mining at Gove in northeast Arnhem Land.
The Commonwealth was granted special leave to appeal to the High Court over claims that the native title case brought by 2019, the late Yunupingu, would invalidate Northern Territory land grants dating back to 1911.
The Gumatj clan performed a traditional song outside a High Court sitting in Darwin ahead of the Commonwealth's appeal of their native title-related victory on Wednesday.
The late Yunupingu's federal case related to a mining lease granted at Gove Peninsula on the west coast of the Gulf of Carpentaria in 1968 to the Swiss-Australian consortium Nabalco.
Dr Donaghue said the Federal Court decision would create an "arbitrary and invidious" divide between native title holders as those in the Northern Territory would potentially receive far greater economic value to their claims,
The lead barrister for the Gumatj, Arthur Moses SC, previously submitted in writing there was "no evidentiary foundation for the Commonwealth's (claim) as to the 'vast' scale of liabilities that would arise beyond the present case".
Mr Moses stated any successful claims would be the result of profound harm caused to Indigenous people in the Northern Territory due to dispossession of their land.
"This court would not be intimidated by the prospect that its function of interpreting and applying the constitution ... may occasion fiscal inconvenience to the Commonwealth," Mr Moses stated.
The special sitting of the High Court in Darwin is due to hear the Commonwealth's appeal over three days.
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