A contentious theory I've often heard advanced is that if you told the police in any major metropolis "One hundred people. You know who they are. Go round them up," and they actually went out and got The Usual Suspects off the street at the same time, that crime in the burg in question would virtually dry up overnight
...and wonders what readers think about that notion. She's asking for input from law enforcement, not from random assholes with excessive self-esteem, so I won't leave a mess of my own in her comments.
But it sounds like a common species of wishful thinking: "The government could trivially fix this problem if only they had arbitrary powers."
Look at it that way, and ask yourself when any government with arbitrary powers ever fixed anything. Or more specifically, when any police force with arbitrary powers ever put a stop to anything.
Some law enforcement types may believe they could do it. Personally, I think they're mistaken.