The Democratic-controlled legislature passed Senate Bill 25-005, titled the “Worker Protection Collective Bargaining” bill, even though Polis, who’s also a Democrat, previously signaled he wouldn’t support it.

Colorado requires a second vote and 75 percent approval when negotiating a union security agreement clause. The bill would have eliminated that second vote, making it easier to unionize.

The governor, in a veto letter sent to lawmakers Friday, said that while he’s pro-union, the state should maintain its higher threshold for mandatory union dues deductions.

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“At its core this is about who has a say in whether union dues are deducted from employee paychecks,” he wrote. “To my mind, mandatory dues deduction should require a high bar of both participation and support, particularly at a time when hardworking Coloradans are concerned about the cost of groceries, the economy, and their job security.”

He added, “To be clear, I believe there must be a high threshold of worker participation and approval to allow for bargaining over mandatory wage deduction. And SB 25-005 does not satisfy that threshold, which is why I am vetoing the bill. Nonetheless, I was and remain open to changes to the Labor Peace Act.”

Unions panned the governor’s veto as siding with corporations.

“Colorado-based [United Auto Workers] members, like those on strike at Lockheed Martin, know workers get the strength to fight corporate greed and improve their working conditions when they join unions,” the UAW said in a post on X, formerly known as Twitter. “SHAME on Gov Polis for showing he is on the side of corporations by vetoing the Worker Protection Act.”

Colorado Worker Rights United, a coalition of labor groups, responded to the veto, saying the governor sided “with corporate lobbyists and billionaire-backed interests over Colorado’s working families.”

“The bill would have removed an unnecessary and harmful barrier that prevents workers from forming strong unions and negotiating for better pay, benefits, and safety on the job,” the group added.

The coalition said it plans on backing a “just cause” ballot initiative for 2026, which “would prevent employers from firing workers without a documented reason.”

The Colorado Chamber of Commerce, which opposed SB 25-005, praised the governor’s veto, saying that while the business community tried to negotiate a compromise with labor groups, they didn’t come to an agreement.

“Unfortunately, we were not able to find agreement with the unions, and we applaud the governor for standing with employees across Colorado who deserve a say in how they spend their hard-earned paychecks,” Chamber President and CEO Loren Furman said in a statement. “Jobs and livelihoods should not be put at risk because a worker chooses not to support union officials who they do not feel represent them or may use their dues to support political causes they disagree with.

“SB 5 would have also threatened our statewide business climate at a time when we should be fostering a competitive economy. We want Colorado to be a top state where business leaders choose to invest and create jobs, and vetoing SB 5 preserves the unique labor laws that set us apart from other states.”