Bukkit

Use the config command (/cfganvil [disable/enable/addmax/removemax] [enchantment] <max-level>) For [enchantment] use the localized enchantment names (case sensitive)

Disable an enchantment:

/cfganvil disable [enchantment]

Enable an enchantment:

/cfganvil enable [enchantment]

Set a max-level to an enchantment:

/cfganvil addmax [enchantment] [max-level]

Remove a max-level from an enchantment:

/cfganvil removemax [enchantment]

Alternatively you can edit the config.cfg: If you want to disable one enchantment just set the false in

enchantment.forbidden.<enchant>=false

to true.

If you want to lower the max level of enchantments that can transferred from the second slot to the resulting item chance

enchantment.maxLevel.<enchant>=x

to

enchantment.maxLevel.<enchant>=y