Western Australian Premier Mark McGowan says his government could intervene if a conservationist-led Supreme Court action against oil and gas company Woodside has adverse findings for the state.

The comments came as protesters blocked off a road leading to Woodside's Burrup Peninsula facility in opposition to a planned expansion of its liquefied natural gas operations.

The Supreme Court challenge, set to be heard in December, would see the Conservation Council of WA (CCWA) seek to overturn environmental approvals provided to Woodside's $16.5 billion Scarborough project, which includes expanding its Pluto plant on the peninsula in WA's north.

Mr McGowan said while he would let next month's court action run its course, he would not let it affect industries if the environment approval was found to be invalid.

"We can't have scores of industries close down because of a court ruling, so the state government will do what it has to do to make sure industries stay open," Mr McGowan said.

"We want to keep the lights on and make sure our hospitals continue to function."

The Scarborough project has been labelled Australia's biggest new fossil fuel investment in nearly a decade and is expected to emit millions of tonnes of greenhouse gas annually.

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Its "scope three" emissions, which come from when customers burn the gas, are expected to equal 866.5 million tonnes over Scarborough's expected field life, according to Woodside.

A 430-kilometre pipeline will also be built, linking the offshore gas resource to the mainland where the gas will be processed.

Mr McGowan said on Tuesday he would take legal advice on what to do, but said it was possible his government could step in.

"If the choice is we're going to close down all the industry in the state and turn off the lights and not have any jobs, well, obviously [we would step in]," he said.

But director of energy at the Grattan Institute, Tony Wood, said if the court upheld the CCWA's action, it would not shutdown the gas industry overnight.

Mr Wood said it could result in a reduction in LNG projects over time, but at some point LNG projects would not go ahead anyway given the push towards reducing greenhouse gas emissions.

Legislation an option for government

UWA professor Alex Gardner, who specialises in environmental law, said the WA government could introduce legislation into parliament that could effectively overturn a court decision.

 "I think the Premier [in his comments] commits to seeking legal advice to ensure the Woodside Scarborough project could proceed," Professor Gardner said.

He said if the CCWA court action was successful — and Woodside did not have legal authority to process Scarborough gas at the Pluto plant — the company could either restart its environmental impact assessment process, or the government could introduce legislation authorising the project's current environmental approvals.

Protesters block access to site

On Wednesday morning, protesters locked themselves to concrete barrels and used a car and caravan to block the Burrup Peninsula road where Woodside facilities are located.

The car was spray painted with the words "Shut Down Scarborough Gas".

Police closed the road and a specialist team was called in to deal with the protesters.

In a statement, a spokesperson for Woodside said there was currently no impact on production.

"Woodside respects people's rights to protest peacefully and lawfully but actions such as these that endanger the safety of others go beyond those rights," the statement read.