Bouncers arn't illegal. What they are is a pain in the backside (when used with a vhost) if the use of them is for the purpose of ban evasion because you can simply log out, change the vhost and then log back in again. Some networks, including mine do not allow them for that reason.
Your IP or Hostname, whatever aplies at the time, is provided by and assigned by your ISP, there is no normal subscriber based control over this. ISPs quite often have many IP ranges that they assign hostnames to, while some if their IP ranges will not resolve.