It should be on record that both times Lethal has been banned, it was made clear that it was a temporary ban. The second time, for requesting a download in the FTP forum (which, argue all you want, that is what your words implied), *MIGHT* have been let slide if it had not come so soon after coming off his first temp ban.
And to answer the original question, the warning system is something that has been added to more recent updates of the Invision Power Board system. The staff, admins, and mods are going to be utilizing this system along with temporary bans as has been done in the past to help keep things running smoothly and keep members aware of how close they are to a permanant ban.