The mayor of Amsterdam this week announced a ban on smoking marijuana -- at school, the AP reports. Strictly speaking he has formalised a restriction that has always existed in Holland’s liberal drug regime but it has been difficult for schools to enforce the policy when students smoked on or near campus and challenged administrators to do anything about it.

Have the folks who voted to legalise pot in Washington State and Colorado, USA, thought about that? Kids turning up to school stoned, or well on the way?

In Colorado, where 55 percent of voters said yes to legalisation in the recent election, Democrat Governor John Hickenlooper declared the weed legal quietly on Monday. He had personally opposed the measure.

“I could have made a bigger deal out of it, you know, tried to make a hoopla out of it,” Hickenlooper told reporters after the marijuana declaration.

“But if we are concerned about young people thinking that this ... is really in some way a tacit endorsement, that’s it’s OK to smoke pot — we’re trying to mitigate that as much as possible,” he said.

The state’s law limits possession of marijuana to persons over 21. Details of how it will be regulated, and how state legalisation interacts with federal law making the drug illegal, have yet to be worked out.

Even in the Netherlands marijuana is technically illegal, but police can’t prosecute people for possession of small amounts.

That's the loophole that made possible Amsterdam's famed "coffee shops" — cafes where marijuana is sold openly. But it has also had the unwanted side effect that Dutch children are frequently exposed to the drug in public areas.

After a change in national law, the city will now be able to declare as of Jan. 1 "no toking zones" — areas like schools and playgrounds where weed-smoking is forbidden — under a public nuisance ordinance. Police can then levy fines against students or anybody else who flouts the rules.

As with open prostitution, many of the Dutch have grown tired of the degraded culture that “tolerance” has brought to their cities. Southern cities such as Maastricht, that have been flooded with dealers from Belgium and Germany who drive across the border to buy weed in bulk, have lobbied for a “weed pass” that would have blocked tourists from buying marijuana, but a draft law has been ditched by the new government. Amsterdam opposed the measure because one in three tourists who come to the capital try marijuana while there, it is claimed.

So, to keep tourists and adults happy authorities have to devote resources, such as police, to maintaining pot-free zones for school kids -- youths who may rightly despise such compromises and flout them at every opportunity.

The AP report notes that, “After several decades of the tolerance policy, Dutch marijuana usage rates are in the middle of international norms, higher than those in neighboring Germany, but lower than those in France, Britain or the United States.”

What we need to know is how this drug culture is affecting the young.