By what authority? Their "prophet" got some golden tablets (which have never been revealed) and made up religious rituals with a markedly Masonic taint.
"Soon after joining Freemasonry, Smith introduced a temple endowment ceremony including a number of symbolic elements that were very similar to those in Freemasonry. Smith remained a Freemason until his death; however, later leaders in the movement have distanced themselves from Freemasonry."
https://en.wikipedia.org/wiki/Mormonism_and_Freemasonry