The book I am using is Doctrine and Covenants Student Manual (Religion 324 and 325) copyrights 1981, 2001. Page 346 in reference to D&C 134:4, 9. The Relation of Religion and Human Law.
President Heber J. Grant (7th President of church) said:
"One of the fundamental articles of faith promulgated by the Prophet Joseph Smith was:'We claim the privilege of worshiping Almighty God according to the dictates of our own conscience; and allow all men the same privilege, let them worship how, where or what they may'
"But we claim absolutely no right, no prerogative whatever to interfere with any other people.(Conference Report, Apr 1921)
Elder John Widtsoe: the Prophet Joseph Smith advocated that "a good government must secure for every citizen the free exercise of conscience. Matters of belief or religious practice should not interfered with, unless they oppose laws for the common good. There should be NO MINGLING OF RELIGIOUS INFLUENCE WITH CIVIL GOVERNMENTS." (Joseph Smith, P. 215)
<I added caps for emphasis>