PEPPER:
"May I ask what is your interpretation of "forced by necessity"?"
Though I'm not a Muslim, I'll take a stab at it.
Forced necessity might mean being forced to eat pork because there is no other food or meat available.
Unlike the proscriptions in the Judaic books of Deuteronomy or Leviticus, Islam seems to give a measured proscription against pork which allows some lattitude.
It is similar to the old Catholic proscriptions against eating red meat on Fridays. The sick, or aged, or those in need or other circumstance where "willfull disobedience" was not a factor (like forgetting say) would not be commiting a 'venal sin' (as opposed to a 'mortal' sin) - in Catholic theological parlance.