The Land and Environment Court has reserved judgment following a judicial review of the Independent Planning Commission's rejection of a thermal coal mine in the Bylong Valley.
The commission ruled in September 2019 that the mine proposed by Korean energy company KEPCO was not in the public interest.
KEPCO told the court this week that the commission did not properly consider a number of environmental impacts, did not follow the correct procedures and that it was denied procedural fairness.
The Environmental Defenders Office, which represented the Bylong Valley Protection Alliance, argued that no legal errors were made and the commission's decision should not be set aside.
"The assessment process before the commission included extensive evidence that there would be up to a 9 metre drawdown of groundwater, that prime agricultural land cannot be rehabilitated, and that the downstream greenhouse gas emissions of this proposed mine would contribute to dangerous climate change, which culminated in the commission deciding that these impacts would not be in the public interest," EDO Special Counsel Rana Koroglu said.
"We argued that the commission's reasons, and all the evidence before it during the assessment process, show that they properly considered these environmental and social impacts and did so lawfully.
"We also argued that it was permissible for the commission to follow the lead of the court to refuse the Rocky Hill coal mine at Gloucester on account of the likely environmental and social impacts not being in the public interest."
Bylong Valley Protection Alliance President Phil Kennedy said the area was home to the top 3.5 per cent of agricultural land in the state and KEPCO's mine proposal placed an important resource in jeopardy.
"We need food security in this country more than we need foreign multinationals digging up one off resources," Mr Kennedy said.
"The Bylong Valley is a unique little valley - there are underground water streams running between four and six metres below the surface that we're able to tap for food security and fodder production."