Legislation (Tashree') is the (sole) Right of Allah

The meaning of Tashree' (legislation) is (the guidelines/rules) that Allah has revealed for His slaves, like the way (Manhaj) they should follow in beliefs and actions, Tahleel (making things Halaal) and Tahreem (making things Haraam). Thus, it is not allowed for anyone to proclaim anything Halaal unless Allah declares it Halaal, or proclaim anything Haraam unless Allah declares it Haraam. Allah says, “Say not concerning that which your tongues put forth falsely, 'This is lawful and this is forbidden,' so as to invent lies against Allah.” [Soorah an-Nahl (16): 116] 

“Say (O Muhammad to these polytheist), ‘Tell me, what provision Allah has sent down to you! And you have made of it lawful and unlawful.’ Say (O Muhammad), ‘Has Allah permitted you (to do so), or do you invent a lie against Allah?’” [Soorah Yunus (10): 59] 

Allah has thus forbidden Tahleel and Tahreem without a proof from the Book and the Sunnah. He has informed us that it is a lie against Allah just like He informed us that he, who makes something obligatory or forbidden without a proof has made himself a partner with Allah in something that is special of Him Alone, and it is Tashree' (legislation). Allah says, “Or have they partners with Allah (false gods), who have instituted for them a religion which Allah has not allowed.” [Soorah ash-Shuraa (42): 21] 

He, who obeys such a Musharri' (one, who makes Tashree') other than Allah and he knows it and is pleased with it, then he has associated a partner with Allah. Allah says, “If you obey them, then you would indeed be Mushrikoon.” [Soorah al-An'aam (6): 121] meaning, he who follows those who make Halaal (permissible) what Allah has made Haraam (prohibited) - he has committed Shirk. 

Allah has informed us that those who followed the monks and rabbis in their making Halaal what Allah had made Haraam and their making Haraam what Allah had made Haraam - that they had taken their monks as gods besides Allah. Allah says, “They (Jews and Christians) took their rabbis and their monks to be their lords besides Allah...” [Soorah at-Tawbah (9): 31] 

When Adee Ibn Hatim heard this verse, he said, “O Messenger of Allah. We didn't worship them.” 

The Messenger of Allah said, “Did they not make Haraam what Allah made Halaal and you all made it Haraam, and they made Halaal what Allah made Haraam and you all made it Halaal?” 

He replied, “Certainly.”

The Prophet of Allah said, “That is your worship to them.” [At- Tirmidhee (3/247)] 

Shaikh Abdur-Rahman Ibn Hasan said, “In this Hadeeth, is a proof that obedience to monks and rabbis while disobeying Allah is worshiping them. It is Major Shirk which Allah does not forgive, as Allah says at the end of the verse, “while they (Jews and Christians) were commanded to worship none but One Deity. La ilaha illa Huwa (none has the right to be worshiped but He). Praise and glory be to Him, (far above is He) from having the partners they associate (with Him).” [Soorah at-Tawbah (9): 31]

Similar is the Saying of Allah, “Eat not (O believers) of that (meat) on which Allah's Name has not been pronounced (at the time of the slaughtering of the animal), for, surely it is Fisq (a sin and disobedience of Allah). And certainly, the Shayateen (devils) do inspire their friends (from mankind) to dispute with you, and if you obey them [by making al-Maytatah (a dead animal) legal by eating it], then you would indeed be Mushrikoon (polytheist) [because they (devils and their friends) made lawful to you to eat that which Allah has made unlawful to eat and you obeyed them by considering it lawful to eat, and by doing so you worshiped them, and to worship others besides Allah is polytheism].” [Soorah al-An'aam (6): 121] 

Many people fall into this with regards to those whom they make Taqleed of (i.e., blind-following) due to their lack of concern for a proof (from the Book and the Sunnah) when the person they make Taqleed of differs (with the Qur'aan and the Sunnah ). Such an act is from this form of Shirk (i.e., Shirk in Tashree’).” 

So, adherence to the Legislation of Allah and abandoning the Legislation of other than Him is from the prerequisites of La ilaha illAllah. And Allah is the Source of help.