CHANNEL MODE b

Usage: MODE <channel> +|-b [<nickname|nick!user@host>]
b - Ban
Will ban the specified user from joining the channel. When used by itself with no hostmask it will list the bans that are in a channel. Valid hostmasks include nickname!user@host. When a user is banned his ability to speak in the channel is removed. You can use this in events to limit a persons ability to cause problems.
Privilege: channel operator
Examples:
/mode #movies +b
/mode #movies +b bot*!*@*.offenderhost.com