A US court has revoked air pollution permits for a huge plastics plant in a region of Louisiana known as Cancer Alley and ruled that they would have violated environmental rules.

People living near the proposed petrochemical complex in St James parish have been fighting against the plans for years and hailed the decision as a victory for environmental justice.

The permits had been issued by the Louisiana department of environmental quality to FG LA, a member of the Taiwanese conglomerate Formosa Plastics Group.

FG LA’s proposed $9.4bn “Sunshine Project” is being designed to produce polyethylene, polypropylene, polymer and ethylene glycol which are used in a range of everyday products. If built, it would be one of the largest production facilities for plastics and plastic feedstocks in the world.

It would also roughly double toxic emissions in its local area and, according to environmentalists, release up to 13m tonnes of greenhouse gases a year to become one of the largest single sources of carbon emissions in the US.

The site on which it is planned is in the heart of Cancer Alley, an area along the Mississippi River which already accounts for about a quarter of petrochemical production in the US and has some of the worst air quality.

Residents of towns along this corridor are also largely Black and face significant health risks.

The Cancer Alley region is the subject of an ongoing reporting series by the Guardian called Cancer Town.

Earlier this week, a Louisiana district court determined that emissions from the proposed plant would violate federal air standards and threaten public health, and that in approving them, the department failed in its duty to protect the public from environmental harm.

Judge Trudy M White said FG LA “failed to demonstrate that its emissions ‘would not cause or contribute to’ violations of the federal air standards”. And the agency’s decision to issue the air permit anyway “violated the Clean Air Act permitting law” it was obligated to apply.

She also said the agency violated its public trust duty to avoid environmental harm by authorising potential public health violations “without offering evidence to show it had avoided the risk to the maximum extent possible”.

Moreover, these duties are not limited to health impacts; White said the Louisiana department of environmental quality “must take special care to consider the impact of climate-driven disasters fueled by greenhouse gases on environmental justice communities and their ability to recover”.

The US army corps of engineers had already ordered a more thorough environmental assessment of Formosa’s project after acknowledging errors in its original analysis. This followed legal challenges brought by campaigners, part of a growing trend of lawsuits being brought to try to halt the local and global impacts of plastic production.

Jane Patton, campaign manager for plastics and petrochemicals for the Center for International Environmental Law (CIEL) and a lifelong Louisiana resident, said she was breathing a sigh of relief.

“I know that my family and community, and communities throughout the state, will be much safer without another industrial facility adding to an already deadly toxic burden and deepening environmental injustice,” she said.

Patton was one of the lead authors of a report, published last year, which documented the company’s six-decade-long history of environmental, health, safety and labour violations, including accidents and pollution in multiple countries.

But she said the problem was much bigger than just this one set of permits and this one company. “Every industrial corporation wanting to develop in Louisiana, Appalachia and worldwide should hear what this decision affirms: communities have rights, and we have power – across the globe. Plastics and petrochemical production are not aligned with a climate-safe future or the universal right to a clean, healthy and sustainable environment.”

In a statement, Janile Parks, director of community and government relations for FG LA, said the company “respectfully disagrees” with White’s conclusion and it intends to explore all legal options. “We believe the permits issued to FG by [Louisiana department of environmental quality] are sound and the agency properly performed its duty to protect the environment in the issuance of those air permits.”

The Louisiana department of environmental quality has been approached for comment.