Bismillahi Rahmani Raheem
Many students of Islam, and too many teachers of Islam, claim an-Nisa 4:65 as justification for laws that call for death-for-apostacy, death-for-blasphemy, or death-for-adultery. . .
But no, by the Lord, they can have no (real) Faith,
until they make thee judge in all disputes between them,
and find in their souls no resistance against Thy decisions,
but accept them with the fullest conviction.
-- an-Nisa 4:65
But let us see what Allah has to say on this matter.
How, exactly, was the Prophet(sallallahu alaihi wa salaam) commanded to judge?
Was it by ANYTHING other than the Qur'an?
Those who do not Judge in the light of Qur’an, are KAFIROON
"It was We who revealed the law (to Moses): therein was guidance and light. By its standard have been judged the Jews, by the prophets who bowed (as in Islam) to Allah's will, by the rabbis and the doctors of law: for to them was entrusted the protection of Allah's book, and they were witnesses thereto: therefore fear not men, but fear me, and sell not my signs for a miserable price. If any do fail to judge by (the light of) what Allah hath revealed, they are (no better than) Unbelievers (KAFIROON)"
-- al Ma'idah 5:44
Those who do not judge in the light of Qur’an are ZALIMOON
"We ordained therein for them: "Life for life, eye for eye, nose or nose, ear for ear, tooth for tooth, and wounds equal for equal." But if any one remits the retaliation by way of charity, it is an act of atonement for himself. And if any fail to judge by (the light of) what Allah hath revealed, they are (No better than) wrong-doers (ZALIMOON)"
-- al Ma'idah 5:45
Those who do not judge in the light of Quan, are FISIQOON
"Let the people of the Gospel judge by what Allah hath revealed therein. If any do fail to judge by (the light of) what Allah hath revealed, they are (no better than) those who rebel (FASIQOON)"
-- al Ma'idah 5:47
Muhammad(sallallahu alaihi wa salaam), himself was ordered to judge in the light of Qur’an
"To thee We sent the Scripture in truth, confirming the scripture that came before it, and guarding it in safety: so judge between them by what Allah hath revealed, and follow not their vain desires, diverging from the Truth that hath come to thee. To each among you have we prescribed a law and an open way. If Allah had so willed, He would have made you a single people, but (His plan is) to test you in what He hath given you: so strive as in a race in all virtues. The goal of you all is to Allah. it is He that will show you the truth of the matters in which ye dispute. "
"And this (He commands): Judge thou between them by what Allah hath revealed, and follow not their vain desires, but beware of them lest they beguile thee from any of that (teaching) which Allah hath sent down to thee. And if they turn away, be assured that for some of their crime it is Allah's purpose to punish them. And truly most men are rebellious. "
-- al Ma'idah 5:48 and 5:49
Muhammad(sallallahu alaihi wa salaam), himself was ordered to hold fast to the revelation
So hold thou fast to the Revelation sent down to thee; verily thou art on a Straight Way.
-- az-Zukhruf 43:43
Muhammad(sallallahu alaihi wa salaam) was ordered to follow only the revelation
And follow what is revealed to you and be patient till Allah should give judgment, and He is the best of the judges.
-- Yunus 10:109
And follow what is revealed to you from your Lord; surely Allah is Aware of what you do;
-- al Azhab 33:2
Muhammad(sallallahu alaihi wa salaam) followed only what was revealed to him
Say: "I tell you not that with me are the treasures of Allah, nor do I know what is hidden, nor do I tell you I am an angel. I but follow what is revealed to me." Say: "can the blind be held equal to the seeing?" Will ye then consider not?
-- al An'am 6:50
If thou bring them not a revelation, they say: "Why hast thou not got it together?" Say: "I but follow what is revealed to me from my Lord: this is (nothing but) lights from your Lord, and Guidance, and mercy, for any who have faith."
-- al A'raf 7:203
But when Our Clear Signs are rehearsed unto them, those who rest not their hope on their meeting with Us, Say: "Bring us a reading other than this, or change this," Say: "It is not for me, of my own accord, to change it: I follow naught but what is revealed unto me: if I were to disobey my Lord, I should myself fear the penalty of a Great Day (to come)."
-- Yunus 10:15
The Qur’an was the only thing revealed to Muhammad(sallallahu alaihi wa salaam)
Say: "What thing is most weighty in evidence?" Say: "Allah is witness between me and you; This Qur'an hath been revealed to me by inspiration, that I may warn you and all whom it reaches. Can ye possibly bear witness that besides Allah there is another Allah?" Say: "Nay! I cannot bear witness!" Say: "But in truth He is the one Allah, and I truly am innocent of (your blasphemy of) joining others with Him."
--Al An'am 6:19
We do relate unto thee the most beautiful of stories, in that We reveal to thee this Qur'an: before this, thou too was among those who knew it not.
-- Yusuf 12:3
Muhammad(sallallahu alaihi wa salaam) and future persons "in authority" cannot give any command on their own,
because “Command is for none but Allah”.
"If not Him, ye worship nothing but names which ye have named,- ye and your fathers,- for which Allah hath sent down no authority: the command is for none but Allah. He hath commanded that ye worship none but Him: that is the right religion, but most men understand not..."
-- Yusuf 12:40
And, finally, with a very explicit straightforward concrete statement...
Say: "Allah knows best how long they stayed: with Him is (the knowledge of) the secrets of the heavens and the earth: how clearly He sees, how finely He hears (everything)! They have no protector other than Him; nor does He share His Command with any person whatsoever.
-- al Kahf 18:26
And, as always