Saving a variable client-side (persistently)

[guiismiti]

Using this technique allows you to remotely save a username and password.

[Not talking about the info stealing] So, using this technique you can set cvar values for players. I still don't understand, how exactly can the server use those values? I'm still trying to figure out a way to either use the value of a player's cvar to disconnect a banned player depending on the value of that cvar (which I was told is not possible), or to simply write disconnect in a .cfg file that will later be executed by a banned player.