Colorado Secretary of State Mike Coffman said backers appear to have submitted enough valid signatures to put the "right-to-work" initiative on the ballot, the Rocky Mountain News reported Tuesday.
A Better Colorado, the group campaigning for the measure, issued a statement from Jonathan Coors, one of its key backers, after learning the initiative had been approved.
"It will constitutionally guarantee the basic rights that all Coloradans deserve," said Coors, a member of the Coors brewery family.
The measure would amend the state constitution by eliminating the current process that allows employees to vote on whether they want to establish an all-union shop.
For his part, Gov. Bill Ritter, a Democrat, is hoping to avoid a battle between labor unions and right-to-work backers.
"Governor Ritter remains fully committed to doing everything possible to ensure none of these measures end up on the November ballot," spokesman Evan Dreyer said.
"He continues to feel this type of battle would harm the state's economy at a time when we should be working together to strengthen our businesses and our work force."