I've been to Amsterdam many times when I lived in England. Being legal and sold through licensed 'Coffee Houses' keeps the illegal drugs off the streets.

The law here in the US is so archaic with regards to even drinking alchohol - compared to the rest of the world. I don't see if becoming legal here anytime soon. I say lower the drinking age to 18 too and sell booze on campus at Universities. Rather than the college kids all using fake IDs to buy alchohol off campus and ending up killing themselves on the roads.