Marijuana sales became legal in the state Jan. 1, but resort workers said they noticed people publicly lighting up before that, Vail Daily reported Thursday.
Advising users what they were doing was illegal was sometimes met with rude responses and comments that pot smoking was now legal.
Vail Resorts is located on federal land on Vail Mountain, part of White River Mountain National Forest.
Chris Jarnot, Vail Mountain chief operating officer, said the problem got so bad the resort began training staff members how to handle such situations.
"Many employees weren't sure what to do, so we made these cards to hand out to people to clarify that it's not legal to smoke it on Vail Mountain, and we helped train staff to confront [offenders] and know the laws," Jarnot said.
The cards lay out in bullet-point format the state law about marijuana consumption:
-- It's illegal to smoke in public
-- Adults over 21 can possess up to 1 ounce
-- It's illegal to ski while high and
-- It's prohibited on national forest lands
The city of Vail has joined in. Signs detailing pot regulations have been posted around town and the town's website has added a section of marijuana do's and dont's.
People who don't comply with the rules will have their passes pulled, spokeswoman Liz Biebl said.
Violators could also face fines of as much as $1,000.