'American Idol' Star Joey Cook: Busted For Weed on Tour

4:35 PM PST -- Joey tells TMZ she had the marijuana to treat her epilepsy. She apologizes to her fans for any inconvenience caused from the arrest and says she'll be more cautious of state laws when traveling in the future. Joey says she'll be at her show in Denver tonight.

"American Idol" contestant Joey Cook just got served by the long arm of the law ... getting busted for weed in a Wyoming airport.

Cook was arrested early Friday morning in Rock Springs, WY for possession of marijuana. She spent a brief 5 hours in jail before getting in front of the judge. Court officials tell us Joey paid a $240 fine and was put on 12 months of probation.

TSA found the pot in her luggage as she was trying to fly outta town. She's on tour and has a show in Denver Friday night.

Joey finished in 7th place on the last season of the show.