CHANNEL MODE z

Usage: MODE <channel> +|-z
z - Encrypted
This requires the encryption module. This mode will lock a channel so that only clients that are encrypted will be allowed into the channel. Not even IRC Operators can bypass this mode with the SAJOIN or FJOIN commands.
Operators can bypass this mode by unsetting it with SAMODE and then joining it.
Privilege: channel operator
Examples:
/mode #movies +z