After the first dip, the drug crime ratio rises again, since people remember that getting punished also involves getting caught. Tension between the police and population increases, with more violent lethal arrests, since more people got nothing to lose.
CR is getting a field day/becomes broken and possibly dies in a raid, having a stack of drugs "found" at his home.
Some internet smartass concludes that the buying drugs=murder logic can be applied on the guns industry. Some crazy guy spectacularly kills a gun suppplier to the police, and being clear of his intent that the police are now oppressors.
The US goverment decleare this anti-gun trend to be treason towards the second ammendment, punishable by death. Since drug use is already considered treason, this is easy. The anti gun lobby is rounded up and executed. Civil war erupts.
Traumatized former soldiers are drowning thier memories by alchohol and drugs. A few more entreprenouric soldiers takes control of the drug market with help of their former comrades in arms. One charismatic oppotunistic cynical is using that drug money to finance a successful coup against the surviving US goverment, making a drug lord as the new ruler of the US.
Going more and more speculative the further down I go, but yep it's a really bad idea from the beginning.
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