Some people have static ip's but some also use dynamic ip's. So the next time they log onto the net they may have a different address. That's the only complication.

You can ban certain ip's using LW. A couple of ways to do it. One is to manually add them to a banned list. Go to LW's menu bar >Preferences>Filters>Hosts.
You can also block them by control-clicking on one of those from the search results & selecting Block Host.