I know this is a SERIOUSLY old Thread... but it didn't give me the answer to the initial question, so anyone still wondering and looking for an answer... If you have the essentials Plugin on your Server, use:
/essentials:ban @p[x,y,z,(r,dx,dy,dz)] (Reason)
Using /minecraft:ban will not work because like mentioned above, Command blocks don't run those commands in chat. Although the /scoreboard command can be run in command blocks now.
Once again, I know this is an old thread... just want to give the desired answer for anyone looking NOW...
