SEATTLE — A voter-approved initiative that requires a two-thirds majority of the Legislature to raise taxes or close tax loopholes violates the state constitution, a judge ruled Wednesday.

Initiative 1053 was approved by Washington voters in November 2010 and has since made it difficult for lawmakers to adopt tax increases.

King County Superior Court Judge Bruce E. Heller’s ruling will likely put the measure before the Washington Supreme Court this fall, as both sides agreed in advance that the case would be appealed no matter which way the judge ruled.

Although the court has ruled previously on the constitutionality of state initiatives, this case focuses on whether a supermajority can be implemented through the initiative process or whether an amendment to the Washington Constitution is required.

Heller said in his ruling that the Constitution restricts the Legislature’s and the people’s ability to require a supermajority for passage of tax measures.

Gov. Chris Gregoire said she was pleased with the ruling because it recognizes the uncertainly that has impeded state government in its efforts to find solutions to its financial difficulties

“We needed a court to resolve the uncertainty about the constitutionality of the supermajority vote requirement, one way or another, in order to move forward to solve tough challenges such as education funding,” Gregoire said in a statement.

A coalition including the League of Education Voters, the teacher’s union, parents, taxpayers and lawmakers argued the initiative violates the intent of the state constitution and allows a small segment of the Legislature to overturn the principle of majority rule.

“This lawsuit is another important piece in making sure our kids have all the resources they need to get an excellent education,” said Chris Korsmo, chief executive officer of the League of Education Voters.

The president of the state teacher’s union agreed.

“This decision is a victory for the children of Washington state,” said Mary Lindquist, WEA president.

“If it is upheld, this ruling will pave the way for the Legislature to fully fund K-12 public schools as mandated by the Supreme Court’s McCleary decision and the state Constitution,” said Washington Education Association President Mary Lindquist. “We hope it will be settled soon. Our kids can’t wait any longer.”

Paul Lawrence of the Pacifica Law Group, lead attorney for the coalition, said both sides are asking the Supreme Court to take the issue up quickly. He said they are hoping for a hearing by September and a ruling before the Legislature goes back to work in January.

Fast action by the court is likely, since right now the Legislature can pass any taxes with a simple majority, Lawrence said.

Lawrence characterized Heller’s ruling as “pro-Constitution” not “anti-initiative.”

The sponsor of Initiative 1053, Tim Eyman, said he believes the court has already decided this case three previous times, after voters approved tax initiatives, and each time decided to leave the matter up to the Legislature and the people.

Eyman said he has been asked why he doesn’t just propose a constitutional amendment, but he reminds the voters that the process for such action requires a vote of the Legislature.

“Hope springs eternal. Maybe they’ll find religion. Until that happens, we’ll keep passing initiatives,” Eyman said.

He is gathering votes to get another tax initiative on the ballot this fall and believes the judge’s decision will light a fire under the signature gathering effort for that initiative.