I say, and with God's help: If he knows that the mufti issues a fatwa based on one of the four schools of thought explicitly or through derivation, it is permissible to transfer his fatwa. However, if he issues a fatwa based on his own opinion without a school of thought reference, and claims that he derives it from the Quran and Sunnah, it is not permissible; because these are not considered valid legal rulings. And God knows best.