What is the ruling on acting upon a fatwa transmitted from a trustworthy shaykh regarding disputed jurisprudential issues?

Allah commanded those who do not know to ask the people of knowledge and specialization, as He Almighty said: [So ask the people of the message if you do not know] (An-Nahl: 43). Therefore, it is permissible to act upon the fatwa of a شيخ (Shaykh) if he is qualified in knowledge, religion, piety, and awareness of reality, and if his fatwa is not contradicted by a more authoritative one. However, if he does not possess these qualifications, then it is not permissible to act upon his fatwa. It is not lawful for a mukallaf (accountable person) to do anything until he knows Allah's ruling concerning it and asks the scholars. For conveying a fatwa, it is sufficient to ascertain its authenticity and attribution to its author through a reliable narration. So, if your friend who conveyed the fatwa is trustworthy, that is sufficient for the validity of the narration.