Who is the Haakim-ash-Shara'a?
The Prophet (SAWAW) and Imams (AS) are the actual Haakim-ash-Shara’a; however in the Occultation of our Imam (AJ), learned ulema and mujtahideen are called Haakim-ash-Shara’a.
I want to know about taqlid. Is it an ijtihadi issue or a taqlidi issue?
This is an ijtihadi issue (deduced from interpretation of the holy Quran and Sunnah), and not a taqlidi subject (deduced from following another’s words without demanding proof); because doing taqlid as a result of someone’s taqlid (i.e. following a jurist as a result of following another’s words without demanding proof) is not permitted.
And the proofs of following a jurist are: Man is by nature a sociable being and relies heavily on mutual help from other human beings. If he is ill, he relies on doctor; for law suits, he relies on a lawyer; for getting his clothes done, he relies on a tailor; and for the construction of a building, he relies on a builder. Likewise, if one is not a religious scholar (alim) himself but wants to practice religion in his life, will he not be in need of referring his problems to an alim? If one strives and exerts himself for the truth of this issue, he will come to the conclusion that indeed he is in need of referring his problems to an alim. This natural practice is called taqlid, i.e. رجوع الجاهل الى العالم (referring of an illiterate to an alim).