That's a good question. The more I think about this, I really think taking away the gang's funds is the way to go.
A very strong border deterrent and more enforcement personnel will do a lot. I'd venture to guess that the construction costs (amortized) and personnel costs for a five-fold increase in border control personnel would be much cheaper, long term - say 15 years - than the costs for policing (and prosecuting, and medical care, and...) in the big cities would be.
Chicago's police budget for 2020 is $1.8 Billion. Add in all the other ones and you can see where this thing is. Now, if you can reduce this number by half, you've paid for the Federal expenditure, and you are saving lives. The money saved could be put in budgets for neighborhood improvements, education, job training, etc.
First bold: it's obvious, IMHO. What happened when prohibition ended? The mob violence that sprouted up around illegal liquor disappeared.
This is what happens with EVERY black market. By definition there is competition between providers, and because they can't go to the police to protect their market they need to have their own hired guns to do so. Once you have a couple of literal armies basically in competition for product sales it becomes a turf war, using violence to settle disputes.
Why doesn't this happen with, say, hamburgers? Because if Burger King hired a bunch of goons to go break the windows out of the competing McDonalds and Wendy's franchisees, the goons would be arrested and those burger chains would sue BK for damages.
Second bold: Everyone points to all the horrible things that would happen if we legalized drugs. They might get addicted! (News flash, they already are.) Addicts might ruin their lives! (News flash, they already are.)
But far fewer people point to all the negatives that exist from the War on Drugs. Huge police budgets to handle violence that's caused NOT by the drugs, but by the black market. Huge prison populations and huge cost to incarcerate offenders caused by making the drugs illegal. Huge societal problems when we have underinvestment in certain areas making the drug trade wildly profitable for dealers while going to school and getting out of the 'hood seems like a pipe dream, so young black kids go down that route. Once they get nabbed and have a record? They're screwed down the line as it relates to jobs and finding any other way to better their lives.
Imagine if we didn't have to spend so many of our tax dollars on enormous police budgets and huge prison budgets for a problem that we've created [and can't ever solve] through prohibition? Could we maybe use that money to help fix some of the societal problems that drugs cause?