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

 “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?’” [Surah 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.” [Surah 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.” [Surah 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...” [Surah 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.” [Reported by 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).” [Surah 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.” [Surah 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'an and the Sunnah ). Such an act is from this form of Shirk (i.e. Shirk in Tashree’).” [end quote]

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.