Ibn Ābidīn (1252 AH), a high standing Hanafi faqīh famously known for his marginal commentary on Radd Al-Mukhtār, wrote a versification know as Rasm Al-Mufti (Protocols of Giving Fatwa) which outlines the details of exactly how, and what is obligatory on those who issue fatwa.
He declared at the outset of that poem:
اعلم بأن الواجب اتباع ما * ترجيحه عن أهله قد علما
أو كان ظاهر الواية ولم * يرجّحوا خلاف ذاك فاعلم