When Maine voters went to the polls last November, their ballots asked them to decide whether the state should prohibit construction on the Central Maine Power Companys $1 billion transmission line from Canada. Nearly 60% said yes, retroactively blocking a project that state regulators had already approved.

On Tuesday, Maines high court ruled that the referendum may have violated the utility companys right to build, throwing the New England Clean Energy Connect a lifeline that could reverse the fate of a controversial project one that experts nevertheless say is vital to weaning the United States gas-dependent Northeast off fossil fuels.

The ballot initiatives language retroactively targeting the line would infringe on the projects constitutionally-protected vested rights if the company can demonstrate by a preponderance of the evidence that it engaged in substantial construction of the project in good-faith reliance on the authority granted by the permit before Maine voters approved the initiated bill by public referendum, the Maine Supreme Judicial Court wrote in its ruling.

CMP will need to prove its case before a lower court. Its unclear when those proceedings may begin. But a victory there would likely lead to construction resuming on the partially built line, assuming it comes before the end of 2023 after which Massachusetts, which is paying for the power line, says it will seek alternatives.