Colorado is making so much money from cannabis it's having to give some back to citizens

Residents could see a share of the $50 million collected

Marijuana on sale at a dispensary in Denver, Colorado (Getty)

Colorado's marijuana experiment has been an empirically rousing success thus far, with crime down and tourism up, and now the state has collected so much money in tax from sales of pot that it might be legally obliged to give some back.

The state constitution puts a cap on the amount of tax money that can be taken in before some has to be returned, meaning Coloradans could see a share of the $50 million generated by sales of recreational cannabis.

"I think it's appropriate that we keep the money for marijuana that the voters said that we should," said Republican Senate President Bill Cadman.

"This is a little bit of a different animal. There's a struggle on this one," added Sen. Kevin Grantham, one of the Republican budget writers.

Coloradans may be asked to vote on making marijuana exempt from the tax cap - the money instead being ploughed into more drug education and police training to spot stoned drivers, as marijuana legalisation is designed to pay for itself without dipping into general taxes.

Last month, a Denver police chief confirmed that a year after legalisation "everything is fine", crime has continued to drop and police are going about their business as usual.