PORTLAND, Maine (AP) Maine’s environmental commissioner suspended a permit Tuesday for a $1 billion electricity transmission line, delivering another blow to the project aimed at bringing Canadian hydropower to New England.

Commissioner Melanie Loyzim’s decision comes after Maine residents rebuked the project in a referendum and the developers suspended construction under pressure from the governor.

But the suspension would be lifted if the project’s developers win a legal challenge, Loyzim wrote.

The latest developments follow years of debate over New England Clean Energy Connect, a project aimed at serving as a conduit for up to 1,200 megawatts of hydropower to reach the regional power grid.

The project has pitted environmentalists, politicians and residents against each other in a debate over the region’s renewable energy.

Proponents say big renewable energy projects are necessary to slow climate change. Critics said the environmental benefits were overstated and that the project was destructive to woodlands. They preferred to have smaller renewable projects closer to home.

Opponents called on the commissioner to uphold the people’s will after the referendum vote. Earlier Tuesday, 50 state lawmakers called on Massachusetts Gov. Charlie Baker to do everything in his power to terminate the project, which is funded by Massachusetts ratepayers.

“This project was fatally flawed from the very beginning and it’s time for Massachusetts to choose an alternative option,” said Pete Didisheim, advocacy director for the Natural Resources Council of Maine, which was opposed to the project.

Developers expressed disappointment with the decision, saying the project is needed to reduce carbon emissions and mitigate climate change that environmental regulators described as the “single greatest threat to Maine’s natural environment,” said Thorn Dickinson, president and CEO of the New England Clean Energy Connect.

“We remain committed to the construction of the corridor and the significant reduction of more than three million metric tons of carbon emissions it will bring to Maine and New England annually,” he said in a statement.

The 145-mile (233-kilometer) transmission line would mostly follow existing utility corridors. But a new section needed to be cut through 53 miles (85 kilometers) of woods to reach the Canadian border.

The Maine Department of Environmental Protection had concerns about the permit based on both the referendum vote and a judge’s ruling that nullified a 1-mile leased portion over state land.

Developers have said that it’s possible to reroute the project to avoid the disputed 1-mile portion.

Other agencies that previously signed off on the project included the Maine Public Utilities Commission, the Maine Land Use Planning Commission and the U.S. Army Corps of Engineers.