Proposed works on the Western Highway duplication at Buangor could be postponed once again after the Federal Court "quashed" a federal minister's decision last week.
The court ruled federal environment minister Melissa Price's December decision not to make declarations under the Aboriginal and Torres Strait Islander Heritage Protection Act to protect trees near the Western Highway to be "an error of law".
Jidah Clark and other Djab Wurrung people applied for the court to overturn the decision and grant protection in June last year, with the court taking a stance on Friday.
"In particular, it is conceded that the Respondent (Ms Price) did not afford the Applicants procedural fairness in making the Decision insofar as the Respondent took into account credible, relevant and significant information without putting that information to the Applicants and inviting them to comment on that information," Justice Debra Mortimer wrote in her order.
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Activists set up camp at multiple sites along the highway near Buangor, ensuring any proposed works did not commence.
Elder Aunty Sandra Onus was also an applicant on the order. She said the federal court's decision adds to the string of wins activists have had in recent months.
"We are hoping everything will calm down and work will only be done in the areas we have asked for," she said.
"It is a lot better than all the damage they wanted to do.
"This order from the court means we can try and work through the alternative route we have provided that will significantly lessen the impact the duplication will have on our cultural heritage."
A fresh decision will need to be made by the environment minister.
A stop-work amnesty was agreed upon between Djab Wurrung people's lawyers and Major Road Projects Victoria in late March, with an agreement made by both parties no work would commence until after 5pm on Monday, April 22.
"This order will impact how they go about it now I think," she said.
"Despite that, people will stay to make sure nothing will be done to the areas in question.
"We believe what was going to happen was unreasonable and we will stick by that."
Major Roads Projects Victoria was approached for comment.