I've noticed that when you get a sovereign to surrender, any enchantments that they currently have on them don't show up in the list of enchantments on your units.
This means you have no way to remove them. This is especially problematic if they have an enchantment that you can only have on one hero (tireless march), because it still counts as being cast on one of your units, but you have no way to remove it if you want to cast it on somebody else.
