Usage patterns
〈人〉が暴力団に入るfor someone to join a crime syndicate
He ended up joining a crime syndicate when he was young.
〈人〉が暴力団と関係を持つfor someone to have ties with organized crime
It was reported that the company had ties with organized crime.
警察が暴力団を摘発するfor police to crack down on / expose a crime syndicate
Police have been cracking down on that crime syndicate for years.
暴力団の資金源になるto become a funding source for a crime syndicate
This underground lending business apparently funds a crime syndicate.