Controversial new emissions curbs by WA’s environment watchdog will tie up major projects in endless court disputes and imperil developments worth tens of billions of dollars, a legal expert says.

Michael Blakiston, a partner at law firm Gilbert + Tobin, said emissions guidelines released by the Environmental Protection Authority would “open up” big resources developments to the same legal nightmare plaguing the Adani coal project in Queensland.

In a change that has been condemned by industry, the EPA said last week it would require all new projects emitting more than 100,000 tonnes of carbon a year to fully offset the emissions.

Mr Blakiston said although ministers led by Premier Mark McGowan had rejected the EPA’s policy, the State Government could not ignore the agency’s position.

He said the gulf between the EPA’s guidelines and the Government’s position would invite costly and drawn-out legal challenges whenever projects were approved by Cabinet.

“You’ve got the risk that policy, although not something the Government is bound by because it is the Government, it nonetheless has to have regard to it in making a decision,” Mr Blakiston said.

“It’s a fascinating concept where you’ve got a minister sitting there who politically may say ‘I’m not going to consider it’ when the law requires him to consider it.

“I don’t know that you can just ignore it because it is a policy of a body that has been charged with a responsibility.”

According to Mr Blakiston, a pipeline of multibillion-dollar WA projects including Woodside’s Browse and Scarborough LNG developments were likely to be captured by the new guidelines.

He said there was a risk of such projects getting drawn into a legal quagmire which could threaten their prospects of going ahead.

“These bigger projects often sit there for an extended period of time waiting for a whole lot of things to come together to enable them to be developed,” he said.

“Market is number one — the commodity cycle and where you are in it.

“You could quite easily have a major project development that should be developed that then stalls through court actions through these sorts of issues.

“And although you may ultimately win the in the court, where you are in the economic cycle or the funding cycle may be such that it can’t get developed.

“To me that’s really where there’s a lot of harm that can happen.”