That reminds me of a pamphlet I was reading in Amsterdam back in 2000. (The details on that trip are sketchy, but I remember the pamphlet.)
It was quite clear about not peeing in the streets and staying the hell out of the canals, but there was advice for what to do if you get too high.
It also said something very close to "If someone is trying to sell you something you don't want, or if you have an argument with a prostitute, please come to the police. You will not surprise or embarrass us. We know why you're here."