FARAH, Afghanistan — When the problems riddling Afghan society are listed — violence, insecurity, corruption, religious fundamentalism — one dominating factor is usually left out: the influence of customary law.

In Afghanistan, there are three principal legal references: constitutional law, the Quran and the system of customary law known as Farhang, the most dominant and strictest version of what is called Pashtunwali (the way of the Pashtuns).

Originally an ancient honor code, Farhang ensures the dominance of the oldest male of any household, followed by married sons, unmarried sons and grandsons, then wives (with the youngest at the bottom). Collective decisions are taken by patriarchs in councils called jirgas, where all have to be in agreement.