Question: Does the Qur’an contain all of Islamic law?

Answer: No, it contains the general moral principles of the law 

Question: What’s the relationship of hadiths and the Qur’an in Islamic law?

Answer: The hadiths explain the details of the Qur’an's law which are not available in the book

Question: Who interprets the Qur’an?

Answer: The Prophet Muhammad (s) and his Ahl al-Bayt (as) 

Question: What is Islamic law’s most important source of law?

Answer: The Qur’an

Question: What is the second most important source of law after the Qur’an?

Answer: The hadiths of the Prophet (s) and his Ahl al-Bayt (as)