AMSTERDAM (AP) — 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.