The First Question
Is it permissible for the student of knowledge to suffice with the declarations of the scholars of the past as to whether a saying of the Prophet, صلى الله عليه وسلم, is weak or authentic? For example, he reads the checking of Haafidh al-Iraaqi where he says, “This hadith is authentic.” So is it permissible for him to suffice with that and the same with Imaam Ahmad or other than him?
Shaikh al-Albaani: “This matter resembles blind following in Islamic jurisprudence (fiqh). It is sufficient for the student of knowledge to listen to and act upon an opinion of one of the Imaams who are followed, and by that I do not only mean the four [famous ones], since there are more, by the Grace of Allaah, the Mighty and Majestic.
We say: [This is so] since it is not possible for all students of knowledge to be on the same level of ability in discerning the truth in those matters where the people have differed. So it is enough for the student of knowledge to implement the aayah, “So ask those who know the Scripture if you know not.” [Surah an-Nahl (16): 43]
So if there are people of knowledge who are alive then he should ask them and embrace their answer, and if there is not a scholar who is alive for him to question, and he knows that a certain scholar from those who are followed has a certain opinion then he can follow him. And in this he is safe from any reproach or blame even if in reality the opinion that he followed is a mistake because he has implemented what was mentioned in the aayah as being obligatory upon him, “So ask those who know the Scripture if you know not.”
But this is based upon certain premises–there is one condition to this, which is that it is not evident to him that the opinion he is following is a mistake. And knowing whether the opinion he is following is incorrect or not can be done by the student doing some personal research if he has the capability of doing so, or it can become known by the direction of another scholar whom he trusts and in whose knowledge he trusts. What is important is that it is permissible for the student of knowledge to blindly follow a scholar if the mistake [in that opinion] is not clear to him and he himself is not capable of clarifying whether [the chosen opinion] is correct or incorrect …” 
[ Footnote here by Amr Abdul-Mun’im Salim the one who compiled and explained the book the question is taken from, he said, “In other words, that he should not take this blind following to be religion. Rather whenever the mistake of the scholar or the Imaam becomes clear to him, it is obligatory for him to shun the opinion in which he is mistaken, whether it is with regard to matters of rulings or the creed, or that which is particular to declaring hadiths to be authentic or weak. And Shaikh al-Albaani has another very important religious verdict [fatwaa] concerning this topic in the book, Fataawaa Madinah, no., 32 on pages 42-43 …”] [it has been translated and can be read below after this answer].
Shaikh al-Albaani continues, “Likewise, totally, is the answer regarding the student of knowledge, he finds an Imaam from the Imaams of the Muslims or a preserver of hadith who authenticates hadith and declares others to be weak, then it is sufficient for this student of knowledge to follow this verifier [who declares hadiths to be authentic or weak] as long as two conditions are met, just as we have mentioned regarding the issue of [blind following] in fiqh:
1) The first condition: That he does not know it to be a mistake, since what is intended by this condition–whether it is hadith or fiqh–is that he does not follow his desires and thus say, “So and so gave me this religious verdict and the matter is closed …” [even though while saying this in reality] he feels some uneasiness in his soul, and the Prophet, صلى الله عليه وسلم, said, “Question your heart even if the mufti gives you his fatwa.” 
[ Footnote of Amr Abdul-Mun’im Salim, “Reported through different paths of narration the most authentic of which is the one reported by Imaam Ahmad (17922) with an authentic chain of narration from the hadith of Waabisah ibn Ma’bad, may Allaah be pleased with him, and the relevant part of that hadith is, “Righteousness is that which gives delight to your heart and sin is that which wavers in your heart, even if the people give you religious verdicts [fatwaas] concerning it.” ]
Shaikh al-Albaani continues, “This is the first condition, i.e., that he does not know that the opinion is a mistake–whether it is regarding the declaration of a hadith to be authentic or weak, or whether it is regarding the permissibility of something or its forbiddance.
2) the second condition: That he himself is not capable of verifying the authenticity or inauthenticity of the particular hadith in question, so this is something permissible–since we cannot burden all of the people [by saying that they must] become capable of reaching the level of ijtihaad or that they become scholars.” 
[ Footnote here by Amr Abdul-Mun’im Salim who said, “That is because if someone reaches the level of being capable of making ijtihaad and he acquires the tools of this knowledge, then it is not permissible for him to blindly follow anyone rather it is then obligatory upon him to make ijtihaad in the declaring of hadiths to be authentic or weak, but it is permissible for him to look at the rulings of the Imaams and the criticisers of hadith to pick from them that which is in accordance with the truth, so that he does not isolate himself with his opinion from their opinion.”]
The Second Question
“What is the proof concerning the forbiddance of blind following?”
Shaikh al-Albaani said, “I do not know of any proof that states that blind following is haraam, rather blind following is a necessity for the one who has no knowledge. And Allaah, the one free from all defects and the Most High, said, “So ask those who know the Scripture if you know not.” Therefore, this aayah placed the Muslims into two categories as regards knowledge:
i) the scholar and it made obligatory upon him to answer the questioner
ii) those who do not know, and it made asking the scholars obligatory upon them.
So if a person from the common folk came to a scholar and asked him about something and the scholar answered him, then this man has implemented the aayah.
And maybe what is intended is something other than what was mentioned in the question [directed to me] and that is the forbiddance of actively splitting into sects and groups; i.e., that a person take his religion from one of schools of thought that are followed and then he totally [refuses] to look at what the other schools of thought might say or at what the sayings of other scholars are–so it is this blind following of schools of thought which is then taken as religion that is not permitted because it opposes the proofs from the Book and the Sunnah.
And the people of knowledge place the people into three categories:
1) the mujtahid
2) the follower on clear proof and insight and
3) the blind follower, and it is this category that most of the people fall into.
As such we cannot say that, “Blind following is haraam,” [that] is only when blind following is taken as religion, as for blind following in general then it is not permissible to declare it to be forbidden.” 
[ Footnote here by Amr Abdul-Mun’im Salim who said, “And what has been said here is also said concerning taking the opinion of a scholar concerning the declaration of a hadith to be weak or authentic, with the condition that the status/rank of that scholar in relation to that knowledge be borne in mind. So such declarations of whether a hadith is authentic or weak are not taken from a scholar of fiqh who does not know [the science of] hadith criticism. Just as the declaration of whether a hadith is authentic cannot be relied upon when it comes from someone among the scholars of hadith or the hadith preservers who is known as being lenient; just as it is not possible to take the declaration that a hadith is weak from someone is known as being overly-strict. In fact this is a correct rule [established] by those known for their moderation and justice along with their knowledge of the principles of this profession and who are known for their practise of it which established their ability to exercise their judgement in arriving at a religious ruling [ijtihaad] concerning the criticism and chains of narration and their texts.”]
Taken from Al-Fataawaa al-Kuwaitiyyah, compiled by Amr Abdul-Mun’im Saleem, pp. 81-83.