كُلُّ مَا لَا تَحُلُّهُ الْحَيَاةُ لَا يَحُلُّهُ الْمَوْتُ
Translation: What life does not permeate is not affected in the same way by death.
Hanafi reasoning uses this principle for the purity of hair, bones and certain hard parts. Impurity arising from death is not automatically assigned to every part lacking that living, blood-bearing quality.
The rule does not nullify separate restrictions such as the intrinsic impurity attributed to pigs.