Traditional Owners and the Conservation Council of WA have lost their fight against a proposed uranium mine that the Environmental Protection Authority refused to back, saying risks to subterranean fauna in the project area were too great.
Former state environment minister Albert Jacob approved Cameco's Yeelirrie mine plan in January 2017, just 16 days before the pre-election caretaker mode began.
Together with members of the Tjiwarl native title group, CCWA challenged the approval in the Supreme Court but lost, and on Wednesday had their the Court of Appeal challenge dismissed.
Traditional Owner Vicki Abdullah said the native title group was disappointed, but taking the case to court had exposed problems with WA's environmental laws.
"We won't give up - our country is too important. We will continue to fight for Yeelirrie and to change the laws, " Ms Abdullah said.
CCWA director Piers Verstegen said the judgment was appalling and demonstrated WA's environmental laws urgently needed to be strengthened.
"This case has confirmed our worst fears - that it is legally admissible for a minister to sign off on a project against the advice of the EPA and in the knowledge that it would cause the extinction of multiple species, " he said.
"We will consider options for further appeal of this decision.
"The mining company can expect a long, expensive process if they want to continue pursuing plans to mine uranium at Yeelirrie."