"This is one of the first long-term blockades of its kind in Australia's history and like the mining companies, we have plenty of tricks up our sleeve," Mr Moylan said in August, as he and fellow campaigner Murray Drechsler set up the forest teepee that would be their home.

The two had only spoken over the internet, but a shared concern for Leard State Forest - the planned site of three enormous coalmines -brought them to the bush camp, where they invited others to join them. Their fellow protesters soon included locals from the Boggabri district, visitors from Sydney, and Bill Ryan, a 90-year-old veteran of the Kokoda Track fighting in World War II, and Mr Ryan's 63-year-old son, Colin.

"I can promise that mine management will certainly know we are about and we're not afraid to take them on in a number of ways which we are not prepared to disclose yet,'' Mr Drechsler said in August.

As northern NSW baked in 40-degree temperatures this week, Mr Moylan was also feeling the heat from the Australian Securities and Investments Commission.

Last Saturday, he used his laptop computer to draw up a fake press release purporting to be from ANZ Bank, saying the financial institution had withdrawn financial support for a proposed Whitehaven Coal mine in the forest.

When he sent it to journalists on Monday morning, and impersonated an ANZ employee, the company's stock temporarily crashed by nearly 9 per cent - equivalent to $314 million.

Mr Moylan has not been charged, but potential offences could lead to fines of $495,000 and up to 10 years in jail. An ASIC investigator made an unannounced visit to the Leard Forest campsite this week, seizing the laptop and mobile phone Mr Moylan used for the hoax.

Usually outspoken and boisterous, Mr Moylan was far more subdued on Thursday, as the potential consequences sank in.

"I have no experience of ASIC, but then I don't think they have any experience of activism with just cause, or civil disobedience, like this situation," he said. "They usually deal with millionaires who try to cheat other millionaires.''

The 24-year-old already has a lengthy history of activism, having been involved in several flamboyant climate change-related protests at coal and aluminium sites in NSW. While a student representative at Newcastle University, he was also a prominent campaigner for better public transport and student rights.

There was speculation among climate change activists that the bank and the coal company would seek to make an example of Mr Moylan. Some drew a comparison with the case of Tim DeChristopher, a US climate activist who posed as a bidder at an auction for oil and gas resources, and outbid actual energy companies to stop them drilling virgin land.

Mr DeChristopher was charged with making false statements and, despite large protests in the US, was jailed for two years in July 2011.