schwim
4
Or use one of the hundreds of thousands of VPN IPs available to him to immediately reconnect.
License and SteamID are the generally accepted best method of blocking someone. I’ve never heard of spoofing game licenses. I’d be interested in hearing more about this if someone knows.
Relating to your problem, however, perhaps an automated method of kicking and banning them is your best solution. If you have something that can detect it and immediately kick him, he’ll quickly grow tired of the effort and move on to another target.
Take a look at salty’s tokenizer. It takes care of the kicking for you when something is detected.