You could fuel the health system instead

In November 2018, former defence secretary Gavin Williamson introduced a zero tolerance approach for drug use, saying it was the only way to ensure excellence was maintained as he highlighted that the purchase of illicit substances fuelled organised crime.

via https://www.theguardian.com/uk-news/2020/aug/24/rise-in-number-of-british-soldiers-being-sacked-for-drug-use

Instead of powering organised crime, you could tax it, and fuel the health system.