Attorney General Ken Salazar, tapped as a special prosecutor by Gov. Bill Owens at the height of the recruiting scandal, said a "thorough review" by his task force resulted in a unanimous decision against charges.
"As with many criminal investigations, these matters will remain open in the event that the nature of evidence of the sexual assault allegation changes in the future," Salazar said in a statement.
He did not immediately return a call seeking comment. The task force will continue its investigation concerning other potential criminal matters involving the Colorado football team and its recruiting program.
The university and a Board of Regents panel are also investigating allegations that sex and alcohol were used to entice recruits to the Boulder campus. At least eight women had accused football players or recruits of rape since 1997, though no criminal charges were filed.
Three of the women have sued the school in federal court, saying its failure to rein in the athletes contributed to their rapes in 2001. They are seeking unspecified damages and sweeping changes at the school.