What is siyasah shar'iyyah and what is the ruler's role in setting rulings based on public interest, including on child marriage?

Summary

This Bayan Linnas introduces the discussion of child marriage from the perspective of siyasah shar'iyyah. The supreme ruler is described as a religious office succeeding the prophetic duty of governing the community, since many Islamic rulings can only be carried out through the ruler's authority. A category of flexible governance rulings is left to the ruler's ijtihad according to the community's interests and circumstances. Siyasah shar'iyyah is defined as the ruler's action based on public interest, provided it does not contradict the fundamentals of religion, even without a specific textual proof.

Written in our own words from the original fatwa — check the source before acting on it.