In a revelation, Joseph was told that he had been given the right to translate by God.
Revelation Book 1, 1-2, The Joseph Smith Papers website, accessed July 16, 2021
. . . behold thou art Joseph & thou wast chosen to do the work of the Lord but because of transgression thou mayest fall. . . .& when thou deliveredst up that Which that which God had given thee right to Translate thou deliveredest up that which was Sacred into the hands of a wicked man . . . this is the reason that thou hast lost thy Privileges for a Season . . .