God has sent guidance & laws through his Messengers - Prophet (s).
 We are required to know them and submit to these teachings, out of free will/choice given to us. 
We can then fulfill the purpose of life, worship, and elevate our soul, to obtain salvation and eternal Rewards.
 The Laws (Fiqh / Shariah) regulate and guide ALL aspects of Life 
Sources of Islamic Laws
The Islamic Laws are derived from:
- Holy Quran and
 - Traditions (Hadith) of Infallible Ahlulbayt(as)
 
Following(Taqlid)of Contemporary Experts Maraje is therefore Logical.
Fiqh -Law Books of Maraje Highest Ranking Scholars