Colorado’s tourists would be able to buy as much marijuana as residents if a bill moving through the legislature passes.

The measure repeals Colorado’s unique-in-the-nation 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 identification.

The purchasing limits were established in 2013 to prevent marijuana diversion out of state.

Colorado pot regulators now say that tourists carrying small amounts of pot home aren’t the state’s main marijuana-diversion problem.

Instead, state regulators and local law enforcement point to underground pot growers as the most likely source of sending pot to states where the drug isn’t legal.

Colorado’s Marijuana Enforcement Division, which oversees pot shops, has never cited a retailer for selling a tourist more than a quarter-ounce of pot.

But the industry fears that new possession limits on concentrated and edible pot due to take effect this fall would make it harder for retailers to keep track. That’s because the new rules don’t consider leafy pot amounts to be the same as, say, pot brownies or hash oil or a skin lotion infused with marijuana’s active ingredient.

“We’d have to hire math professors to work in the dispensaries” to keep track of purchasing limits, said Mark Slaugh, head of the Colorado Cannabis Business Alliance.

Removal of the tiered purchase limits is part of a routine renewal of Colorado’s pot regulations. That renewal has passed the state House and is awaiting approval in the state Senate, where an initial committee approved the change Wednesday.