Second chance for Sydney's Sirius building

Sydney's iconic Sirius building will get a second chance at a heritage listing after the Land and Environment Court ruled the NSW government made legal errors when it chose not to protect it.

Acting Justice Simon Molesworth, delivering his verdict on Tuesday, said then-heritage minister Mark Speakman had not properly considered a recommendation by the Heritage Council to list Sirius on the register in 2016.

The minister decided against registering the building at The Rocks because it would cause "undue financial hardship" for the building's owners.

But Justice Molesworth concluded even if registering Sirius decreased its sale value, that did not constitute financial hardship.

"I have concluded that the minister did misdirect himself when he interpreted the words 'financial hardship'... when he erroneously equated financial hardship with a diminution in the sale value of Sirius," Justice Molesworth said.

He said some iconic structures were so valuable to society their financial burdens could never be "undue" and should be carried at all costs.

He considered two other iconic landmarks around Sydney Harbour - the Opera House and Harbour Bridge.

"The financial impost associated with such iconic heritage items might be enormous, never cease, and cause the owner to suffer financial hardship," the court heard.

"But however onerous, any financial hardship would, arguably, never be considered to be 'undue'."

Justice Molesworth did not make a decision on whether Sirius held a similar level of value, and stopped short of ordering the minister to list it on the Heritage Register.

However, he rendered the existing decision invalid and ordered the government to remake a decision based on law.

He also ordered the government pay costs to the Millers Point Community Association, which is fighting the decision to sell off Sirius to private developers.

Members of community group Save Our Sirius cheered as the verdict was handed down.

"Sirius has been temporarily saved," SOS chairman Shaun Carter said outside court.

"What we say not only to the minister and the Premier, Gladys (Berejiklian), this is a moment when we ask you to hit pause on the demolition and sale of Sirius and sit down with us so we can talk about the heritage listing."

He said the city was desperately short of social and affordable housing and Sirius, which was designed to fulfil this demand, had sat empty for three years.