Around the time Smith's revelatory authority is challenged by Hiram Page and a prophetess named Hubble (see page 48-49 of Charisma Under Pressure), he produced D&C 43: 2-7 which states (emphasis added):
2 For behold, verily, verily, I say unto you, that ye have received a commandment for a law unto my church, through him [Joseph Smith] whom I have appointed unto you to receive commandments and revelations from my hand. 3 And this ye shall know assuredly—that there is none other appointed unto you to receive commandments and revelations until he [Joseph Smith, from now on "JS"] be taken, if he abide in me. 4 But verily, verily, I say unto you, that none else shall be appointed unto this gift except it be through him [JS]; for if it be taken from him [JS] he [JS] shall not have power except to appoint another in his stead. 5 And this shall be a law unto you, that ye receive not the teachings of any that shall come before you as revelations or commandments; 6 and this I give unto you that you may not be deceived, that you may know they are not of me. 7 For verily I say unto you, that he [someone other than Joseph Smith] that is ordained of me shall come in at the gate and be ordained as I have told you before, to teach those revelations [the published Scripture] which you have received and shall receive through him [Joseph Smith] whom I have appointed.
In other words, if Joseph was to "fall" spiritually, he was to replace himself and ordain another to take his place, but that person acting in his stead was to only teach the published revelations (received through Smith) which are the gateway to true doctrine.
Compare D&C 41:2, wherein the Lord through Smith says that members of the Church are commanded to "assemble yourselves together to agree upon my word; ..." The word being the Scriptures containing the revelations and commandments. Meanwhile the published Scriptures are those which are approved by common consent (see
D&C 26:2).
Note that the Lectures on Faith were accepted as scripture (as the doctrine portion of the origional Doctrine & Covenants) by common consent, but were removed from the scripture cannon by the Brighamite sect around 1920 (which was done without common consent). Meanwhile, the King Follet Discourse was never accepted as scripture by common consent yet used to form Brighamite doctrine, as it has been interpreted by James Talmage in a way to form modern Brighamite dogma; yet some LDS scholar's like Blake Ostler disagree with Talmage's interpretions and dogma.
After dictating the Word of Wisdom (in D&C 89), Joseph Smith occasionally drank beer, wine and smoked a cigar. This is because the Word of Wisdom makes it clear that it was not given by commandment nor constraint; yet later LDS leaders -- around the same time they removed the doctrine of the LDS Church from scripture (The Lectures on Faith) --reinterpreted the Word of Wisdom in a way contrary to the original meaning of the word (see D&C 41:2 quoted above), i.e. in a way contrary to God's clear words in the Word of Wisdom: that says it was not given by commandment nor constraint.
