
Extract the answer to the question from the following context.
Question: Who decides these principles?
Context: Currently, (2004), there are principles of canon law common to the churches within the Anglican Communion; their existence can be factually established; each province or church contributes through its own legal system to the principles of canon law common within the Communion; these principles have a strong persuasive authority and are fundamental to the self-understanding of each of the churches of the Communion; these principles have a living force, and contain in themselves the possibility of further development; and the existence of these principles both demonstrates unity and promotes unity within the Anglican Communion.

each province or church contributes through its own legal system to the principles of canon law common within the Communion
