The key part:

They had a question they wanted a court to answer. Is the state government responsible for the greenhouse gas emissions from the burning of coal after it is sold and exported overseas?

On Wednesday, the high court found that it is.

In a landmark 3-2 ruling, a majority of judges found the Independent Planning Commission of NSW failed to consider imposing conditions aimed at minimising these emissions – known as scope 3 emissions – to the greatest extent possible when it approved MACH Energy’s coalmine expansion.

Huge outcome in principle.

It would be trivially easy for the government to amend the law to say it is not required to consider scope 3 emissions, or to resubmit this approval by saying "we considered imposing scope 3 emissions restrictions and decided against it". And if this had happened in Queensland under the openly corrupt Crisafulli government I have no doubt that would happen. But perhaps in NSW there's some hope that it will hold.

But as a matter of law, this finding is awesome.