And a drug war also encourages manufacturing and selling drugs that are as potent as possible, like fentanyl. The same happened with Prohibition: the underground market was all hard liquor, not beer.
EDIT:
This also occurs at the street level. I've read stories of people not wanting to talk to the police about a murder because they are afraid the police will find some weed and arrest them instead.
Sadly a common example is the question whether to call 911 in case of domestic violence for the same reason.
It's unfortunate that average street gangsters are even less disciplined than the cops. You'd love to see a firefight between a properly trained squad and police. The cops will run even faster than that coward sheriff when the very disturbed fellow shot up Parkland High School.