Bukkit

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