Don't you mean the first to laugh?
Also I would help, however I imagine it is going to be device signature (maybe mac address of network card as a basic means, or maybe a more complete device signature), account level and also server side bans which means manually unbanning via annoying spoofing*, people already using dummy/throwaway accounts and hacking into online servers to change info (done in the past for some things, probably not worth it for pokemon) or making third party servers (not done but a potential option I would like to see play out). I don't know if the game needs active internet to work but some kind of gets GPS but not 3g/wifi mode a la cardholder not present in credit cards might be an option.
*I doubt it has improved since the 3ds streetpass spoofing that saw various people have to change macs and mess around with their android devices at similar levels. I don't have a 3ds and I do have proper networking gear so eh really.