Um, you can't outlaw people for associations... sorry.
If you can prove that gangs are committing actual crimes, then by all means, arrest them.
Now, all that said, the Chicago gang problem is largely self-inflicted. The city used to be divided by three major gangs, but the Feds in the Obama years busted those gangs up and they were succeeded by a lot of smaller gangs fighting over much smaller areas of turf
Of course, if you really wanted to get rid of the gang problem, legalize drugs and prostitution, and you'd cut off their main sources of revenue.