Following a deceased marja

الفوائد المدنية والشواهد المكية - محمد أمين الإسترآبادي ، السيد نور الدين العاملي - الصفحة ٢٩٩

Al Fawaid al Madniya by Shaikh Muhammad Amin al Astarabadi (ra), Page 299

ما اشتهر بين المتأخرين: من أصحابنا من أن قول الميت كالميت لا يجوز

العمل به بعد موته، المراد به ظنه المبني على استنباط ظني. وأما فتاوى الأخباريين

من أصحابنا فهي مبنية على ما هو صريح الأحاديث أو لازمه البين فلا تموت

بموت المفتي. نعم، بعضها الذي كان مبنيا على حديث ورد في الواقع من باب التقية

ينقطع العمل به إذا ظهر المهدي - صلوات الله وسلامه عليه - وكذلك فتاوى

المتأخرين المبنية على صريح الحديث أو على لازمه البين لا تموت بموت

صاحبها. لكن التمييز بين القسمين صعب على مقلديهم

What is popular among the latter scholars from our companions, that "fatwa of the dead (mujtahid) is like the dead (i.e. redundant), it is not permissible to act on it after his death", this means that his (mujtahid's) supposition is based upon speculative derivation. And as for the fatwas of the akhbaris among our companions, so it is based on what is evident in ahadith or essentially evident, so it does not die (i.e. become redundant) due to the death of the mufti. Yes, some of them are based on hadith stated in the situation of taqiyya, causing abrogation of acting by it when Imam Mahdi (as) appears. And similarly, fatwas of the latter scholars based upon explicit hadith or the essentially evident, does not die (i.e. become redundant) by the death of their issuers. However, distinguishing between them (i.e. between the fatwa based on speculative assumption and the one based upon explicit ahadith) is difficult upon their muqallids (followers).

Translator's note: Among contemporary mujtahids, I have found that Ayatullah Ishaaq Fayyadh conditionally allows doing taqlid of a dead scholar while Ayatullah al udhma Shaikh Muhammad Hussain Dhakkoo al Najafi unconditionally allows doing taqlid of a dead scholar. Below, I'll list their views.

Ayatullah Ishaaq Fayyadh

سؤال(10) : ما هو رأيكم في تقليد الميت أبتداءً ؟
الجواب : لا يجوز تقليد الميت ابتداءً ما لم يحرز أنه أعلم الأحياء والأموات

Question 10: What is your view regarding starting taqlid of a dead scholar?

Answer: It is not permissible to start taqlid of a dead scholar unless he harbors that he is a'lam (most learned) among the living and the dead scholars.

http://www.alfayadh.com/site/index.php?show=news&action=article&id=176

Ayatullah al udhma Shaikh Muhammad Hussain Dhakkoo al Najafi

 Qawaneen ush sharia fi fiqh al ja'fri

To summarize, in the text above Ayatullah Dhakkoo sahab says that the popular saying that the muftis fatwa becomes redundant upon his death is baseless because the righteous mujtahid would rule as per the Qur'an and hadith and obviously, the Qur'an and hadith do not die with the death of the mujtahid. Of course, if a person's ijtehad is based on his own ra'y (opinion) and qiyas, then it is possible that such mujtahid would realize his errors after his death. But since such mujtahid who rules by his own opinions and qiyas, his ijtehad is not acceptable according to us (Ayt. Dhakkoo) in his life than how can it be acceptable after his death?