By Keith Coffman
DENVER (Reuters) - Colorado's two largest airports have tightened their rules on marijuana possession after the state became the first in the nation to allow recreational pot stores to operate, airport officials said on Thursday.
Noting that marijuana remains illegal for any purpose under federal law, under which airports operate, the main airports in Denver and Colorado Springs have issued new policies to penalize anyone caught with cannabis.
At Denver International Airport - the nation's fifth- busiest - first-time offenders will face a $150 fine, rising to $500 for a second offense and $999 for a repeat offender, said airport spokeswoman Laura Coale.
At the Colorado Springs Airport, offenders can be subjected to both fines and imprisonment, interim airport manager Dan Gallagher said in a statement announcing the new rules, which take effect on Friday.
Colorado Springs Police Chief Pete Carey said "amnesty boxes" will be placed at the airport where travelers can leave their pot without being charged. Anyone caught trying to bring pot into prohibited areas will be cited, he said.
Signs will be posted around the airport warning of the possible penalties, the Colorado Springs airport said in a statement. Colorado Springs allows medical marijuana dispensaries, but the city council voted last summer to ban recreational shops.
Both airports make no distinction between the possession of recreational or medical cannabis products.
"Medical marijuana has been legal in Colorado since 2001, and recreational marijuana has been legal here since January first of last year, so I don't understand why these rules are coming out now," said Rachel Gillette, the head of Colorado's chapter of the National Organization for the Reform of Marijuana Laws.
Gillette, who opposes the rules, said it was already illegal to board a plane with cannabis, but the new rule applies to all areas of the airport, including areas that do not require Transportation Security Administration screenings.
Colorado's new law allows residents over the age of 21 to purchase up to an ounce (28 grams) of recreational marijuana. Out-of-state visitors are limited to quarter-ounce (7-gram) purchases, and marijuana bought in Colorado cannot be transported across state lines.
A total of 136 retail stores in Colorado have been granted licenses to sell recreational weed although not all have opened for business yet, according to figures from the state Department of Revenue.
Since recreational pot sales began on January 1, traffic has been brisk at the state's approximately 50 recreational pot shops that are operating, said Betty Aldworth, deputy director of the National Cannabis Industry Association, and a handful of shops have reported running out of inventory.
(Editing by Dan Whitcomb and Eric Walsh)