Colorado tourists would be able to buy as much pot as residents, under a bill moving through the state legislature.

The measure would repeal Colorado's one-of-a-kind tiered purchasing system for marijuana. All adults over 21 are allowed to possess an ounce of marijuana -- but retail pot shops can't sell more than a quarter-ounce in one day to people without Colorado IDs.

The purchasing limits were established in 2013 to prevent marijuana diversion out of state. Lawmakers figured that visiting tourists wouldn't blaze through a full ounce before heading home. An ounce of pot is sometimes compared to a keg of beer because it's difficult for most users to finish in a few days.

A bill nearing approval in the state Legislature repeals the tiered purchasing rules.