WILLIAM BRANGHAM:

This decision not to regulate the supply chain causes several problems: not only do the Dutch lose their chance to tax that side of the business, but more importantly: it's allowed an illegal export market to flourish. A senior police official estimated that 80 percent of the pot grown in the Netherlands gets sent abroad and ends up on the black market.

Another Dutch official said: "We now function as a supplier of drugs for the rest of Europe…we never intended to become one of the major exporters of cannabis to the world."

Officials in ten major Dutch cities have appealed to the government to finally fix this gap in the law, but nothing's happened.

Back in the U.S., Colorado and Washington are regulating the entire pot market – how it's grown, processed, sold and taxed. Their rules were designed to protect consumers, and to ensure none of that legal pot ends up on the illegal market. The irony here of course is that the U.S. – which used to criticize Dutch policy – now has two states implementing even more comprehensive policies than the Dutch ever have.

Back in the Netherlands, the Dutch have continued to refine their policy.

They've stepped up enforcement of coffee shops. Back in the late 90s, there was a concern about too much leniency towards them so stricter rules were written, and violators closed down. No new licenses have been issued in almost 20 years.

The Dutch are also tackling the rising potency of pot – (something both Colorado and Washington want to do as well). Dutch scientists regularly test coffee shop marijuana, and anything over a certain level is considered a hard drug and forbidden for sale.

The Dutch have also had a big national debate about whether 'drug tourism' needs to be reined in.

In the small city of Maastricht, which sits on the Netherlands' southern border with Belgium and Germany, city officials saw an alarming number of foreign visitors crossing into their town with just one destination in mind.

Onno Hoes is the mayor of Maastricht.