DENVER (AP) – State lawmakers opposed to Colorado’s landmark Taxpayer Bill of Rights won another legal victory Friday as the 10th U.S. Circuit Court of Appeals ruled their lawsuit challenging the law can proceed.

The tax limitation law passed by voters in 1992, known as TABOR, requires all tax increases to be approved by voters. The lawmakers argue that deprives them of the right to have a say in tax policy, denying Colorado a republican form of government promised by the U.S. Constitution.

A three-judge panel from the appellate court concluded that the lawmakers have proven they have been injured by the law and the lawsuit should proceed. They didn’t rule on the merits of the case, which will continue in federal court unless Attorney General John Suthers appeals.

“We consider solely standing and the political question doctrine: whether these plaintiffs have suffered a particularized injury not widely shared by the general populace that entitles them to have their case heard by the federal courts, and whether the question presented is purely political in nature and should not be reached by the courts,” the ruling said.

State attorneys argued that the mostly Democratic lawmakers challenging the law didn’t have the right to sue because they were not harmed by the law.

If the lawsuit ultimately succeeds, it could have implications for tax limitation laws in other states, such as California’s Proposition 13.

David Skaggs, a former Democratic congressman, is representing the lawmakers challenging the law. Besides state lawmakers, the defendants also include city council members and school board members from around the state.

It’s the second time the state has lost a bid to stop the lawsuit.

In July 2012, U.S. District Judge William J. Martinez rejected a motion from Suthers on behalf of Gov. John Hickenlooper to throw out the case, leading to the 10th Circuit appeal. Former lawmakers also joined the lawsuit, but Martinez and the appellate court have only ruled that current lawmakers should be able to sue.

Besides votes on tax hikes, TABOR also restricts state and local government revenues from growing by more than inflation plus population growth without voter approval.

Under TABOR, lawmakers have been reluctant to ask voters to raise taxes, often opting instead to raise fees that don’t require approval. In 2005, lawmakers did ask voters to suspend the revenue limit from 2006 to 2010 to help the state recover from a drop in revenue during the previous recession, and voters agreed.

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