Firstly, a Muslim should worship Allah only in the way which is proven by evidence from Qur’aan and Sunnah. Such evidence may be quite evident which most people can know, or it may be obscure and they way to know it is the ijtihad (meticulous derivation of Islamic ruling from the evidences present) of scholars who are inheritor of the Prophets (i.e. they secured religious knowledge). If someone is one of these scholars Mujtahid scholars (i.e. those who can derive rulings of Islamic Law from the evidences themselves due to their scholarly acumen), he cannot but follow the conclusion which he reached through his ijtihaad in matters subject to ijtihaad. If he is not a mujtahid, he should follow (do taqleed) of a scholar whom he deems fit to be followed, since Allah said, “….so ask of those who know the Scripture, if you know not.” [Surah Al-Nahl, verse 43]
Secondly, some secondary derivative legal rulings (al-tafri’aat), which do not have any evidence from the Qur’aan and Sunnah to back them up, nor are the result of ijtihaad of reliable scholars are not at all part of Islam, and Muslim should not act on them, since Allah said, “And follow not that of which you have no knowledge. Verily! The hearing, and the sight, and the heart, of each of those you will be questioned (by Allah).” [Surah Bani Israel, verse 36]. However, it is not permissible for us to take such baseless rulings as a means to attack scholars of Islamic jurisprudence (fiqh).
Allah knows best.
Translated for Islam-QA