OLYMPIA, WA – It was more than a year ago when voters approved a ballot measure to protect access to natural gas service in homes and other buildings, undercutting Washington’s efforts to transition away from fossil fuels.

The fate of that initiative now rests with the state Supreme Court.

The justices heard arguments Thursday morning in a challenge environmental groups and local governments brought against Initiative 2066. They argue the measure is unconstitutional because it covers more than a single subject and does not contain the full text of state laws it would alter.

Last March, a King County Superior Court judge agreed. Backers of the initiative appealed, landing the case at the state’s highest court.

The Building Industry Association of Washington, a trade group for homebuilders, sponsored the initiative and is defending it alongside the state. The state has to defend the initiative because it was passed by voters, even though lawmakers have previously approved policies that it conflicts with.

“The people of Washington enacted 2066 for one singular purpose: to ensure that they had the option of gas as a source of energy for their homes and their buildings,” said Callie Castillo, an attorney for the Building Industry Association.

The pro-gas initiative passed in November 2024 with 51.7% of the statewide vote. It includes provisions to ensure customers will have a supply of natural gas, for appliances like furnaces and stoves, and that providers will continue to have consumer demand, proponents said in a court filing.

“Initiative 2066 is constitutional,” said Karl Smith, deputy solicitor general at the Washington State Office of the Attorney General. “Each of the provisions is germane to the general subject of protecting access to and use of natural gas.”

But a coalition of environmental and clean energy organizations, along with the city of Seattle and King County, contends that the ballot measure “does far more” than protect access to natural gas.

They claim that the multi-part initiative, which ran 21 pages, would change building code rules, air pollution regulation authority, repeal provisions to accelerate Puget Sound Energy’s transition away from natural gas and limit local governments’ ability to establish energy efficiency standards.

Paul Lawrence, attorney for the groups and local governments challenging the initiative, called the provisions “silent amendments” to existing law.

“‘Stop the gas ban,’ was BIAW’s motto for having people sign and vote for this,” said Lawrence, adding that the pitch for the initiative was “combined with much broader attacks” on state climate policy and building codes.

In a friend-of-the-court brief filed in the case, former Gov. Jay Inslee, who championed climate policy during his time in office, along with Sen. Rebecca Saldaña, D-Seattle, Rep. Beth Doglio, D-Olympia, and House Majority Leader Joe Fitzgibbon, D-West Seattle, argued the initiative would dismantle years of policy to curb air pollution, protect public health and transition to cleaner energy.

Doglio, the House and Environment Energy Committee chair, sponsored the legislation related to Puget Sound Energy that the initiative would roll back.

The building codes the measure targets were designed to get more electric heat pumps installed in newly built homes and other buildings.

“Do the voters want to preserve access to natural gas and also undermine several statutes that have been enacted over the years to promote a policy of looking at sustainable, clean energy housing?” Lawrence said in court Thursday, as he argued that the initiative was too broad.

He expressed confidence afterward that the Supreme Court would reach the same conclusion as the lower court judge.

Greg Lane, executive vice president of the Building Industry Association of Washington, said the group hopes that “the court will recognize the urgency of this case” and provide a ruling swiftly.

“The 546,000 citizens who signed the initiative and the nearly 2 million voters who supported its passage deserve a resolution soon,” he said.

The Supreme Court is expected to rule on the case in three to six months.

This story first appeared on Washington State Standard.