DENVER (AP) — A federal judge has dismissed a long-running lawsuit challenging Colorado’s strict tax and spending limits as unconstitutional but more appeals are possible.

U.S. District Judge Raymond Moore ruled Thursday that none of the former or current elected officials, educators or citizens challenging the 1992 Taxpayer’s Bill or Rights or TABOR have proved they were harmed by it. As a result, he said they don’t have the right to challenge the voter-approved measure in court.

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TABOR also requires tax increases to be approved by voters. Challengers say that violates the U.S. Constitution, which guarantees a republican form of government in each state where elected officials make decisions.

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The lawsuit was filed in 2011. Along the way, part of it was considered by the U.S. Supreme Court, which sent the case back to court in Denver.

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