Polygamy (plural marriages) is illegal in all 50 U.S. states and outlying territories.

I would like to know the legal justification for why this is. Are there records showing how judges interpreted how the possibility of a plural marriage did or did not accord with general legal rights, i.e., the Constitution? What explanation did they give for why they rule that it is legally just to make plural marriage illegal?

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    The prohibition was well established in English law and tradition many centuries before the US came into existence. It's unlikely that you'll find much in court records. You might have better luck looking at legislation and the records of legislative debates.
    – phoog
    Commented Jan 5 at 8:54
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    I don't think you'll find court proceedings for this because this doesn't seem to be something that a court will do. The job of a court is not to justify why law makers make certain laws. The job of the court is to take a law that was written by law makers and interpret what they mean. That being said, in the US, marriage is a legal status (and comes with tax implications) so likely limiting this legal status was to avoid a tax loophole. If they remove the tax implications associated with marriage, they will likely lift restrictions on marriage as well.
    – uberhaxed
    Commented Jan 5 at 16:22
  • @uberhaxed however, if anyone in the US has challenged a law prohibiting polygamy on constitutional grounds, and if the court could not avoid the constitutional question by deciding the case on some other question, then the court would have to decide whether the prohibition is constitutional or not, and would have to explain its reasoning.
    – phoog
    Commented Jan 7 at 16:06
  • @phoog it might be worth noting that slavery was constitutional until made explicitly illegal. I don't think a judge would take a case that seems trivial.
    – uberhaxed
    Commented Jan 7 at 17:12

2 Answers 2


The answer from JMS is substantially correct, but doesn't provide the judicial opinion source that the question indicates that it seeks.

One of the court decisions most comprehensively recapping the judicial and legislative history of U.S. polygamy law is the 93 page ruling on a motion for summary judgment of the U.S. District Court judge for the District of Utah in the case of Brown v. Buhman, 947 F.Supp.2d 1170 (D. Utah 2013), which was reversed on procedural grounds in the U.S. Court of Appeals for the 10th Circuit in 2016 (sometimes known as the "Sister Wives" case because the Plaintiffs were the stars of a reality TV show about a polygamous family, of the same name).



Are there court proceedings records detailing why polygamy has been made illegal (in the U.S.)?

Short Answer:

All fifty states have passed anti-polygamy laws since the mid 1800's, some had such laws earlier. Utah, however decriminalized the practice in 2020, reduced polygamy from a third-degree felony to a minor infraction on May 13, 2020. Historically the practice was associated with Slavery and like slavery the practice was eliminated through war. The Utah war in 1858. The Civil war to end the practice of slavery would kick off in April of 1861.

The two major pieces of national legislation are the

  • Morrill Anti-Bigamy Act, 1862
  • Edmunds Act, 1882

both outlawed the practice of polygamy in federal territories. States were left to sort out their own laws.

sources for each are below.


Polygamy in the United States was associated and sorted out around the same time as slavery was. And Like Slavery the country went to war in 1858 to purge polygamy from one if it's territories. The Utah War. Many abolitionists who famously opposed slavery also opposed polygamy. The first national act of anti-polygamy legislation, the Morrill Anti-Bigamy Act, was passed by Congress in 1862. The act was named after Republican Senator Justin Smith Morrill who was known for his staunch opposition to the practice of both slavery and polygamy. It was known as the twin relics of barbarism Slavery and Polygamy.

Polygamy became a significant issue in the United States as early as 1852, when the Mormon Church (Latter-day Saints) declared that polygamy was "part of their doctrine."

Official sanction by the Church of Jesus Christ of Latter-day Saints

The Mormon doctrine of plural wives was officially announced by one of the Twelve Apostles, Orson Pratt, and church president Brigham Young in a special conference of the elders of the LDS Church assembled in the Salt Lake Tabernacle on 28 August 1852, and reprinted in the Deseret News Extra the following day.6 The announcement came nine years after the purported original revelation by Joseph Smith, and five years after the Mormon exodus to the Salt Lake Valley following Smith's death in Carthage, Illinois.

Utah would be denied statehood over the issue for nearly four decades until their leaders renounced the practice in 1890. Statehood followed six years later.

Legal Justification? Each of the 50 states passed laws outlawing Polygamy. In 1882 the Federal government passed the Edmunds Act, which outlawed Polygamy in the Federal Territories.

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