Amsterdam's mayor said Wednesday he would formally ban students from smoking marijuana at school, making the Dutch capital the first city in the Netherlands to do so. Eberhard van der Laan's introduction of a law that in other countries either already exists or seems so obvious it wouldn't even require a rule is the result of the Netherlands' unique drugs policy. Under the "tolerance" principle, marijuana is technically illegal here, 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. City spokeswoman Iris Reshef says schools have always forbidden pot, but found it difficult to enforce the policy when students smoked on or near campus and challenged administrators to do anything about it. "It's not really what you have in mind as an educator, that children would be turning up for class stoned, or drunk either for that matter," she said. But it has been a problem for some schools. 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. The move is closely paired with a decision by the new government to ditch plans for a national "weed pass" that would have blocked tourists from buying marijuana. That was a measure years in the making, and greatly desired by 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. But the weed pass was opposed by Amsterdam, where drug tourists are not generally seen as causing many problems. Last month, Van der Laan proclaimed that coffee shops would stay open for tourists after all. In a letter Wednesday, he noted that one in three tourists who come to Amsterdam try marijuana while they're here, more than previously estimated. Wednesday's decision seems to signal a typically Dutch compromise outcome: the drug will remain available for adults and tourists who want to try it, but access for children will be restricted. 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.