A dam owned by Hydro-Quebec.

THE SUPREME JUDICIAL COURT of Maine on Thursday yanked a referendum question off the November ballot that could have derailed a Massachusetts proposal to import hydro-electricity from Quebec using a power line running from the Canadian border to Lewiston, Maine.

The high court, overturning a lower court’s decision, held that the referendum question was unconstitutional and shouldn’t be allowed on the ballot because it sought to overturn a key regulatory approval of the power line granted by the Maine Public Utilities Commission.

The decision doesn’t end the fight over the power line, but it knocks out one of the major challenges to it. The ballot question, as of several weeks ago, had already become the most expensive in Maine history, with the opposing sides spending tens of millions of dollars appealing to voters. Opponents of the project said their polling indicated the ballot question was likely to pass.

Massachusetts has largely stayed out of the fight, but electric customers in the Bay State set it in motion. Three Massachusetts utilities, acting on behalf of their customers at the Baker administration’s request, agreed to pay nearly $1 billion to the Quebec-owned utility Hydro-Quebec and the Maine utility Central Maine Power to import hydro-electricity into the New England region.

An earlier bid to import the hydro-electricity using a power line through New Hampshire was shot down by regulatory agencies there.

The goal of the hydro-electricity project is to increase the supply of clean energy coming into the region and help reduce greenhouse gas emissions.

Gas-fired power plants in Maine, who saw the power line as a threat to their business, joined forces with environmentalists and sport fishing groups to oppose the power line. Hydro-Quebec and Central Maine Power poured millions of dollars into a campaign supporting the power line, as well as a legal challenge to the ballot question itself.

Their legal challenge said the referendum question was unconstitutional because it violated the separation of powers between the legislative and executive branches of government. In its opinion, the court likened the ballot question to a legislative action initiated by voters instead of lawmakers. The court ruled that the ballot question exceeded the scope of the people’s legislative powers because it sought to overturn an executive branch regulatory decision.

“The initiative at issue here is not legislative in nature because its purpose and effect is to dictate the [Public Utilities] Commission’s exercise of its quasi-judicial executive-agency function in a particular proceeding,” the court’s opinion said. “The resolve would interfere with and vitiate the commission’s fact-finding and adjudicatory function – an executive power conferred on the Commission by the Legislature.”

The decision stunned opponents.

“We are digesting the ruling of the Maine Supreme Court and weighing our options for going forward,” said Adam Cote, an attorney representing opponents of the power line.

Colin Durrant, a spokesman for the Natural Resources Council of Maine, said the environmental group was extremely disappointed. “The vast majority of Maine people oppose the CMP corridor and they deserve an opportunity to vote,” he said. “The CMP corridor would cause irreversible harm to the woods and wildlife of western Maine, providing no benefit to the climate. With federal permits still under consideration and appeals of previous permits underway, this destructive transmission line proposal is far from a done deal.  The Natural Resources Council will continue to pursue every avenue available to defeat this project because it’s a bad deal for Maine.”

Bruce Mohl oversees the production of content and edits reports, along with carrying out his own reporting with a particular focus on transportation, energy, and climate issues. He previously worked...