The Kill Warrant Scanner does a search for bounties across all juridictions, so you can learn about (and possibly claim) bounties that are offered by factions from other systems than the one you're currently in. In your case this fella is a wanted criminal *somewhere* but is not in here, which means that you would get wanted if you attack him. I learned this the not-so-glorious way.
As Heartwork points out, anarchy systems have no ruler thus no law enforcement, everyone is free to shoot anyone and get away with it.