Prevent an object from being destroyed in HABTM relationship

Hello all,

I have the following models:

class Sku < ActiveRecord::Base
has_and_belongs_to_many :options
class Option < ActiveRecord::Base
has_and_belongs_to_many :skus

By default if I destroy an Option any relationships between Options and
Skus will be removed as well.

But, I want to prevent an Option from being destroyed when it is
associated with a Sku in the options_skus table. So the only way to
destroy an Option is to first remove each relationship. Is this
possible to do in the model? Is there a particular Rails way to do it?

Thanks for any help or suggestions you may have!

Ian N.