There were fireworks inside Sydney's Land and Environment Court as two men who took part in illegal land clearing began shouting and heckling before they were fined $100,000.

Key points: The men were found to have conducted illegal land clearing at their Colo property

The men were found to have conducted illegal land clearing at their Colo property Dr Mustapha Kara-Ali and Diaa Kara-Ali ran a religious guild on the land, in Sydney's north west

Dr Mustapha Kara-Ali and Diaa Kara-Ali ran a religious guild on the land, in Sydney's north west They had claimed their property was exempt from Australian law

Brothers Mustapha and Diaa Kara-Ali illegally cleared land and developed on a bush block in Sydney's north west, claiming the Islamic spiritual group they ran on the property was exempt from Australian law.

The pair were asked to leave the courtroom by their lawyer at one stage and came back after they had calmed down.

Hawkesbury City Council took the brothers to the Land and Environment Court in June last year.

From the beginning, the duo refused to take part in court proceedings and ignored orders by the court to stop construction works on the land.

On Thursday, they were convicted of 12 counts of contempt of court.

The Kara-Alis argued they were exempt from Australian law because their spiritual group, Diwan al Dawla, was classed as a basic religious charity.

That claim was not endorsed by the Australia Charities and Not-for-profits Commission, who later stripped the group of its charity status.

The brothers were also accused of locking in a man delivering them court documents by padlocking the gates on the Colo property while he was still inside.

Sorry, this video has expired Council workers arrive at Colo property

In sentencing the two men, Justice Terence Sheahan said the brothers only engaged in the court process "following my reluctant decision to have you arrested … to address the problems you've created", describing their contempt of the court as "flagrant".

In his published reasons, Justice Sheahan said the brothers' claim they do not have to comply with Australian law is false.

"In December 2017, the Australian National Imams Council ('ANIC'), with the assistance of the NSW Judicial Commission, prepared a document entitled 'Explanatory Note on the Judicial Process and Participation of Muslims'," he wrote.

"The note clearly envisages that Muslims in Australia will often be expected to participate in court processes.

"It even stresses that there are many similarities between the Western tradition and the Muslim concept of justice."

But Justice Sheahan pointed out Mustapha Kara-Ali "disowns" that note, quoting him telling the court "that document belongs in the trash bin".

Before and after photos show the loss of vegetation after the men cleared the block. ( Supplied )

The judge also ordered the pair would be fined $2,000 for every month after June this year they failed to remediate the Colo property.

The pair were eligible to appeal or have their fines adjusted.

Outside court, Mustapha Kara-Ali repeated previous claims of religious persecution and said, "our religion is prime".

Ian Dickson, whose son lives in the area, was at court for the sentencing and said it was unfortunate the case had gone on for so long.

"It could have been avoided [by] putting in a DA application as everyone has to do," he said.