Former Auburn deputy mayor Salim Mehajer has won his Supreme Court appeal against a four-month suspension for failing to disclose his financial interest in a property.

In January, the Administrative Appeals Tribunal suspended Cr Mehajer for voting to approve changes to a family company-owned property that added an estimated $1 million to its value.

The Office of Local Government had been investigating whether the 29-year-old breached pecuniary interest laws by failing to declare the interest when he voted to increase floor space ratios on the Auburn building, as well as its height.

The NSW Civil and Administrative Tribunal found Cr Mehajer breached pecuniary interest laws on three occasions — once in 2012 and twice in 2013 - and slammed the councillor for his "hubris".

On Friday, the Supreme Court set aside the decision to suspend him.

The court set aside the decision because of an error in law regarding the interpretation of the phrase "permissible use of land".

But it did not agree to Cr Mehajer's request for a finding that he did not breach the Local Government Act.

Cr Mehajer had some advice for others.

"Do not allow yourselves to be 'bullied' in the face of intimidating aberrations but rather to always fight for your rights," he said in a statement.

He said the decision showed that he was right to fight the suspension.

"I am extremely pleased to say that justice has once again been served, a precedent set and that everyone, including each and every one of you, to believe in yourselves when you know you've committed no wrong," he said.

"Even when council as a whole was suspended I still challenged the 'individual suspension' against myself personally as I whole heartedly believed in the truth and that truth was confirmed today."

Earlier this month, the NSW Government appointed an administrator to run the council while a public inquiry examines allegations of councillors misusing their positions.

The decision to suspend the entire council was criticised at the time as an "abuse of power" by Cr Mehajer, who had already been suspended for breaches of the Local Government Act.

Meanwhile, the administrator of Auburn Council, Viv May, last week rescinded two major developments that were to benefit the controversial councillor.

The tribunal had previously found the property-developer-turned deputy mayor committed other breaches of financial disclosure laws and it suspended him for one month.

But that penalty was also overturned on appeal to the Supreme Court.

Cr Mehajer first made headlines after closing a street for his lavish wedding in August 2015.

He has also been embroiled in a number of legal matters since he came to prominence, including being charged with intimidation.

The Australian Federal Police has also investigated him for electoral fraud offences and the NSW Government has called for him to stand down.