Vice has an interesting video about what happens when neighboring countries have different drug policies. (Uncensored version here.)
While Sweden rigidly sticks to its zero tolerance laws, liberal Denmark introduced drug consumption rooms (DCRs) in 2012, with special areas surrounding them where you won't get arrested for drug possession if it's for personal use. Copenhagen is home to one of the world's largest government funded drug consumption rooms, H17, where users can safely smoke or inject their drugs with clean needles and medical staff on hand.
This has resulted in the local areas being safer and cleaner, as there are no longer thousands of used needles littering the streets. But Denmark's liberal policy has had an unexpected consequence: an influx of heroin users from neighboring Sweden. We find out why Swedish heroin users prefer to sleep rough on the streets of Copenhagen rather than stay in Sweden, and which of these policies is most effective at tackling overdoses.