Safe injection sites are only effective apparently when combined with legalization and/or decriminalization of the drugs injected, source: http://chasingthescream.com/

TLDR: the criminal lifestyle one must pursue to obtain illegal supercharged versions of the drugs is vastly more harmful than the drugs themselves when legalized. I see a lot of parallels here in equating all sex work to sex trafficking. Both sides have their points, but what is the most effective strategy to minimize sex trafficking?