Under the laws passed by Congress, the condition for the admission of Utah into the Union was that they abandon polygamy. In fact, under the Enabling Act, they could be thrown out of the Union if they renege. Same goes for Arizona. And New Mexico. Their state constitutions explicitly say that they cannot reinstitute polygamy without an act of Congress.
(So much for those who claim that marriage issues are not national, federal issues...)
See #119... there is the Supreme Court confirming just what you said...
See #118 (typo) ... there is the Supreme Court confirming just what you said...