The Colorado Supreme Court blocked a proposed ballot initiative on Monday that would have required voter approval for new fees above a certain threshold, while also enshrining a definition of “fee” into the state constitution for the first time.

Chief Justice Monica M. Márquez wrote in the March 9 opinion that a ballot measure could properly accomplish one of those goals or the other, but combining them ran afoul of the constitutional requirement that initiatives contain a single subject.

“Initiative #158 presents a danger of log rolling because it may attract a ‘yes’ vote from voters who support statewide voter approval of fees, but who would not support narrowing the definition of existing and new fees under Colorado law,” she wrote. “Conversely, it could attract support from voters who support changing the existing definition of ‘fee’ throughout Colorado law, but who would not support a new statewide voter approval requirement for certain fees.”

The Taxpayer’s Bill of Rights is a 1992 state constitutional amendment generally requiring voter approval for new taxes or tax rate increases. That mandate does not apply to fees. Neither “taxes” nor “fees” is defined in the Constitution, but court decisions over time have established that fees are primarily intended to defray the costs of providing a service pursuant to a “comprehensive regulatory scheme.”

Initiative #158 was one of nearly two dozen tax-and-fee-related ballot measures proposed in recent months by former Arapahoe County GOP chair Suzanne Taheri and Michael Fields of the conservative Advance Colorado Institute. Although the proposals varied, Initiative #158 contained two primary components: requiring voter approval for most fees that would raise over $100 million in their first five years, and creating a constitutional definition of “fee” for future and existing fees.

The state’s Title Board green-lit Initiative #158 in October, after determining it satisfied the single-subject requirement. The following month, the board adjusted the wording of the summary that would appear to voters if proponents collected enough signatures to place it on the statewide ballot.

Joshua Mantell, director of government affairs for the progressive Bell Policy Center, petitioned for Supreme Court review of the Title Board’s actions. He argued the measure improperly contained two subjects. Taheri countered that Initiative #158 was aimed holistically at closing the “loophole” in TABOR that exempts fees from voter approval.

“To effectuate the purpose of Initiative #158, it is necessary to define ‘fee,'” she wrote for herself and Fields. “No voter surprise will result from the definition of ‘fee’ or the voter approval requirement for new fees enacted by the General Assembly.”

But the Supreme Court agreed with Mantell that the measure’s new constitutional definition of “fee” departed from the judicially created status quo and amounted to a second subject.

“Despite Proponents’ contentions, changing the current definition of ‘fee’ is not necessary to effectuate the purpose of this Initiative,” wrote Márquez. “We see no reason, and Proponents do not explain, why the voter approval requirement would be unenforceable and meaningless without the proposed new definition of ‘fee.'”

“We are grateful the Colorado Supreme Court so thoughtfully considered the issues and agreed that the initiative contained more than one subject and therefore was ineligible to move forward. The process worked as intended and Colorado voters are well-served by this decision,” said Mantell in a statement.

Taheri did not respond to an email seeking comment. Several other revenue-related measures from Taheri and Fields have received Title Board approval, although none have qualified for the ballot yet.