Polygamy is a crime in many liberal countries (such as all 27 countries of the European Union). It is theoretically victimless, however. Why then would a liberal country criminalize it?

Things I can think of:

  • Polygamy is sexist. However, polygamy is not intrinsically sexist, and in most liberal countries, polyandry is just as illegal as polygyny.
  • Polygamy can involve power differentials, historically involving men abusing women. While conceivable, the same can be said of prostitution, and prostitution is legal in many liberal countries.
  • Moot/pointless because if the adults involved are all happy with the arrangement, they can live together without marrying. This is also conceivable, but there are legal advantages to marriage, so it's not entirely moot/pointless.

Related: Why do many liberal countries criminalize incest? which asks about a similar illegal activity.

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    It would be nice if you took into account polyamorous relations which, while lacking official status, may not be as criminalized. Jul 19, 2023 at 1:38
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    @Obie2.0 what's with the "ugly boomer word"? You could equally say that one gags at how many millennial Tinder profiles prattle on about their polyamory. ;-) Jul 19, 2023 at 1:48
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    @ItalianPhilosophers4Monica - The point, made somewhat ironically, is that younger generations will think that the word polygamy sounds ugly because of the association with patriarchal societies, but will end up legalizing it under a different name because the concept dovetails well with a focus on marriage equality.
    – Obie 2.0
    Jul 19, 2023 at 2:32
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    "Polygamy is sexist. However, bigamy is not intrinsically sexist" - no, bigamy is just a special case of polygamy (with n=2).
    – Trang Oul
    Jul 20, 2023 at 5:14
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    Does this answer your question? What purpose do anti-Polygamy laws serve? Or maybe that one should be closed as a duplicate of this, since there's more/better answers here?
    – Bobson
    Jul 20, 2023 at 13:38

8 Answers 8


Old laws change when there is a call for it

This line of questioning "Why to liberal countries criminalise X" should take into account when that law was put in place and whether the countries were liberal at the time. Then we just have the question of "Why do countries have laws that haven't been updated yet?"

In the case of the UK the current law that criminalises bigamy was in Section 57 of the Offences against the Person Act 1861:

Whosoever, being married, shall marry any other person during the life of the former husband or wife, whether the second marriage shall have taken place in England or Ireland or elsewhere, shall be guilty of felony, and being convicted thereof shall be liable

Not a time when the UK would have been considered a liberal country (at least by today's standards). Until the populace sufficiently petitions a government to make changes to laws, they don't.

Bigamy (and incest for that matter) simply aren't things that enough voters are interested in having legalised and plenty would be against. No government wants to put through an unpopular law without sufficient backing. A petition to legalise bigamy and polyamorous marriage currently only has 21 signatories out of a necessary 10,000 for a response and 100,000 it to be considered.

  • Sometimes old laws also change when a fresh look at them lets a constitutional court realize that they are unconstitutional... Jul 20, 2023 at 15:14
  • No need to include incest.
    – paulj
    Jul 21, 2023 at 11:38
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    @paulj This question is part of a set the OP asked, incest was one of the others. Jul 21, 2023 at 13:06
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    In Ireland, the constitution states that marriage can occur between 2 people. An amendment would require referendum and that usually requires a big political push, and the appetite isn't there. Besides, assuming you could get that through (and there would be large resistance) there is, no doubt, a whole host of laws around marriage that work based on the assumption of 2 people (e.g. sharing tax credits, child-related laws, etc.) which would all have to be updated too - it would be a huge undertaking. So rather than a moral objection to polygamy it may be a practical one.
    – komodosp
    Jul 24, 2023 at 9:22

Stability of the society

When a high-status man takes two wives, a lower-status man gets no wife. Those men, denied access to life's most stabilizing and civilizing institution, are unfairly disadvantaged and often turn to behaviors like crime and violence. There are generally higher levels of rape, kidnapping, murder, assault robbery and fraud in polygynous cultures (source). Societies become inherently unstable when effective sex ratios reach something like 120 males to 100 females, such that a sixth of men are surplus commodities in the marriage market (source). That's not a big number.

This is not very directly related to Christianity. Even before Christianity became the official religion of the Roman Empire, Diocletian and Maximian passed strict anti-polygamy laws in 285 AD.

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    It's worth pointing out that in societies where men do routinely take many wives, they are often characterised by high rates of military action which adjusts the sex ratio (and polygamy becomes a functional response to how many men must be allocated to war, without leaving a surplus of unwived men).
    – Steve
    Jul 20, 2023 at 9:48
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    You're equating polygamy (being married to multiple partners) with polygyny (a man being married to multiple women). Historically, polygyny may have been the dominant form of polygamy, but this is also strongly tied to oppression of women and forced marriages. In an equal society where all combinations of polygamy are allowed, the bad effects listed wouldn't really apply. (Although given that the question asks why society is that way it is, historical reasons play a big part.)
    – NotThatGuy
    Jul 20, 2023 at 13:08
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    @NotThatGuy There is a reason why historically polygamy was one man+multiple women and not one woman+multiple men - and it has nothing to do with oppresion of women...One man can have children with multiple women, but one woman cannot have children with multiple men (at least at once). And since desire for offspring is one of the strongest biological urges(and wanting being in a relationship when you don't have a chance of having your offspring is kinda a good way to NOT pass on those traits).So that kind of polygamy will still introduce same instability into your society as having single men.
    – Negdo
    Jul 20, 2023 at 14:54
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    @Negdo Technically a woman can, as there is such a thing as (heteropaternal) superfecundation (two distinct ova fertilized at essentially the same time, possibly by different men; if it's the same father you get what we call fraternal twins). It's pretty rare, though (maybe on the 2-3% level amongst women involved in paternity disputes, so a sample likely biased towards a higher rate), so on a practical level your statement is correct. But it's nice to remember that biology is weird and there's a lot of variety in twins. Jul 20, 2023 at 15:53
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    @Negdo: I'd describe the reason differently: no matter how many women a man sleeps with, any woman will know whether she is the mother of any child sired by her husband. If a woman sleeps with multiple men, however, none of them will have any way of knowing whether they are the father of any of her children.
    – supercat
    Jul 20, 2023 at 17:07

Two reasons spring to mind:

  1. Most (ostensibly) liberal countries are Western: European or colonized by European settlers. That means they were all (at some point) strongly steeped in one of the Abrahamic sects, specifically various forms of Christianity. The Christian faith sees marriage as a union between souls, and so anything that would disrupt the God-granted bond between two souls — extra-marital affairs, divorce, and yes, add-on marriages — was forbidden as a sin. Even as religiosity has declined in the West, that attitude has persisted. It doesn't help that the those modern(ish) groups which have tried to rehabilitate polygamy have all been schismatic Christian sects or blatant cults, and thus roundly criticized by the mainstream.
  2. Polygamy as a historical practice was markedly aristocratic. Multiple wives were the province of the wealthy and politically powerful, whether as a status symbol, an effort to maximize the possibility of male heirs, or as a means to create political or economic alliances. As such, it didn't have much effect on the lower classes, aside from some natural salacious interest. But as the ideals of Liberalism took hold — and yes, before someone else says it, 16th century thinkers likely would have lumped women under 'property rights' — the concept of polygamy became somewhat distasteful. Partly (I think) this was a dismissive contempt that polygamy was a decadent activity of pervy aristocrats or exotic foreigners. But partly I think it was the growing realization that women are only 51% of the population, and if every Freeman Jack set his mind on multiple wives, simple math would lead to massive bloodshed.

Few cultures have ever seriously considered the issue of polyandry, since a woman with multiple male parters was almost universally considered shameful or sinful. But, you know, this is all speculation.

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    The first argument makes sense, but it doesn't clarify why extra-marital affairs and divorce are nowadays legal, but add-on marriages are still a crime.
    – Evargalo
    Jul 19, 2023 at 13:56
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    @Evargalo: Divorce is legal courtesy of Henry VIII and subsequently the Protestant reformation. Henry VII was king just before the onset of the Classical Liberal era, most to the CL thinkers were protestants of one sort or another, and the concept of divorce jibed well with Liberal ideals of personal freedom. Note that Ireland (a staunchly Catholic nation) only legalized abortion in 1995. Jul 19, 2023 at 14:36
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    @Evargalo: Extra-marital affairs are legal (as I see it) because — despite being universally despised — they are hard to adjudicate. Wikipedia's Adultery in English Law points out that jurisdiction waffled between secular and ecclesiastical courts, and punishments ranged from death sentences to fines for men and disfigurement for women to public or private acts of religious penitence to civil torts. Ultimately they settled (1923) on saying that the only legal consequences of adultery was giving grounds for divorce. Jul 19, 2023 at 14:49
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    Judaism most definitely allowed polygamy for 1000 years after the start of Christianity en.wikipedia.org/wiki/Gershom_ben_Judah#Synod_and_bans (who got monogamy from the Romans).
    – RonJohn
    Jul 20, 2023 at 20:37

A partial answer is that, in the US, much of the support for bigamy laws came from opposition to child marriage.

The biggest examples of bigamy in the US has been FLDS members - that is fundamentalist offshoots of the LDS (mormon) Church.

While the LDS church now forbids polygamy, they used to support it (its been argued they only gave it up to avoid persecution). Not every group agreed with these reforms.

Within these FLDS groups, polygamy takes the form of polygany (one husband, multiple wives), with women being "married off" young, usually to much older men. With the women having no say in the matter (or virtually anything else). It is a very barbaric practice and culture.

I don't know if they're still around, but Tapestry Against Polygamy was a group that opposed polygamy for that reason.

  • Did you really want to write that it was support for bigamy laws what came from opposition to child marriage?
    – Ángel
    Jul 21, 2023 at 0:00
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    @Ángel i think by 'bigamy laws' they mean laws against bigamy. So support for outlawing bigamy.
    – Ivana
    Jul 21, 2023 at 7:45

Because this is how their people want to visualize themselves.

In liberal countries, state acts are formed based on public opinion. People form an idea, then they gather as a group, then create pressure on the government to legalize it. Then public representatives take it to the parliament and the act gets passed.

For example,

  1. Same-sex marriage in the Netherlands was legalized a decade ago because people wanted it.

  2. Germany is in favor of LGBTQ right, because the people want it.

  3. People in some countries wanted Marijuana to be legalized, so Marijuana is legal now in many countries.

Why don't people want it to be allowed?

For cultural reasons! Culture is developed on the basis of history and anthropology.

For instance, Western culture suggests women should wear shorter clothes than men. This is unintuitive given that women have more private parts than men. However, the West certainly has their own reasoning which I would not want to dispute.

Similarly, Western culture allows men to have multiple sex partners while they cannot have multiple wives.

If these people can form a sufficiently large group and start a movement in favor of polygamy, the state would surely decriminalize it in the end.

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    It's not allowed because people don't want it to be allowed - ... okay, but why don't people want it to be allowed? It seems you've just described how a democracy works.
    – NotThatGuy
    Jul 20, 2023 at 12:51
  • @NotThatGuy, why don't people want it to be allowed? --- Cultural reasons. Culture is developed on the basis of history and anthropology.
    – user366312
    Jul 20, 2023 at 13:32
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    That...'s still not saying much. What cultural reasons? Which parts of history and anthropology is this based on?
    – NotThatGuy
    Jul 20, 2023 at 13:35
  • @NotThatGuy, check the edit.
    – user366312
    Jul 20, 2023 at 13:36
  • Not entirely: see James K answer. Allowing more then two people to enter a marriage means solving a lot of 'technical' legal problems, and writing specific laws for specific cases. Not just for future 'marriages' but also for existing and maybe even past marriages - what is grandma receives a pension based on the pension plan of grandpa who is dead. Now what if grandma remarries, her spouse marries another two people, one of them marries more people, some of them get divorced, and so on. Who of all these people will get some of that pension?
    – Ivana
    Jul 21, 2023 at 7:52

It's not very romantic but technically marriages are just small scale private unlimited corporations. Meaning a company of 2 people sharing risks, profits and mutual responsibilities. And it's a financial union that is often subsidized by the state.

So it's not a victimless crime, you potentially cheat on the state and on your spouse who now has to cover for your failures but isn't profiting from your profits that you generate with another spouse.

So it's not just polyamory but there are also quite some financial and legal considerations involved in that.

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    This only explains why current marriage laws are unsuitable for more than two members. But you could reform laws to properly and fairly scale with ≥2 members.
    – Michael
    Jul 20, 2023 at 11:25
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    Really, this perspective is a strong argument that it should be simple for a legal change to allow for polygamy, since currently more than two people can found and run a business. If a marriage is a financial structure, then that structure can be adapted to be like other financial structures. Jul 20, 2023 at 15:36
  • this also seems to imply or presume some sort of an equal partnership, which a marriage always hasn't been (esp. if the wife is considered the man's "property"), and also with prenups being a thing, the part about a financial union need not be a thing. And if there's no financial structure, there should be no obstacle in taking another partner to the marriage.
    – ilkkachu
    Jul 20, 2023 at 19:14
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    @Michael not easily. going beyond 2 people is a giant leap and introduces numerous problems and circumstances that simply do not exist when you are only dealing with 2 people. Mathematically, with two people you have only 1 interaction (AB), with three people you have 4 (AB, BC, AC, ABC). It's an expenitional problem, and an utter nightmare to try compared to the already massive problems a normal divorce involves. Which is why there's basically no historical examples (even in polygamous societies, who only had 1 or 2 of the people having any real rights in divorce)
    – eps
    Jul 21, 2023 at 0:35
  • Cheating on a spouse or falsifying legal relationships is a crime in itself. The context in which that crime occurs (if marital) is not a crime.
    – pygosceles
    Jul 21, 2023 at 18:35

Polygamy was a target of a major political movement

No answer to this question is complete without mention of the notable Morrill anti-Bigamy Act of 1862, the Edmunds Act of 1882 and the Edmunds-Tucker Act of 1887.

The express purpose of those acts was to restrict the religious practice of plural marriage and other activities by members of the Church of Jesus Christ of Latter-day Saints, who at that time had largely emigrated to the Utah Territory. The acts criminalized polygamy and enforced sanctions against those who practiced it or taught it, even to the extent of disincorporating the church and endeavoring to make its founders and practitioners felons.

The notion of polygamy being evil or reprehensible began to be more widespread and vehement in the United States some decades earlier as a direct response to the founding of this church and the practice of its religion, which did involve a number of cases of and teachings about polygamy. The indignation against polygamy became galvanized into a mainstream political movement when the 1856 Republican National Convention advanced the notion that it was a "barbaric relic" as a contemptible twin to human slavery, that had to be eradicated.

The founder of the Church of Jesus Christ of Latter-day Saints, Joseph Smith, had just been assassinated twelve years prior in 1844 by a mob in Illinois, in part spurred on by rumors of polygamy and myriad libelous claims against him. After his death, the saints spent two years preparing to move West. They were headed for what was then Mexican territory to find a refuge beyond the borders of the United States where they could practice their religion without being mobbed and murdered for their beliefs.

The geopolitical aspect of this change did not last long; the Mexican Cession through the Guadalupe-Hidalgo Treaty of 1848 brought them once again within the borders of the United States, subject to its politics and policies.

What is ironic about the "twin relics" claim of the Republican Convention is that Smith was assassinated not long after he began campaigning for president of the United States; notably his platform included the abolition of slavery. He was the first US presidential candidate to be assassinated. Some historians opine that his anti-slavery stance may have contributed significantly towards the impetus for his assassination. The later assassination of Abraham Lincoln over this same subject lends credibility to that hypothesis. Abraham Lincoln is widely hailed as the father of the Republican party.

On the basis of this understanding, did the two alleged "barbarisms" really belong together?

Relation of anti-polygamy movement to Christianity

The claim in at least one other answer that polygamy was disfavored in Christian societies ignores some very important facts about the Christian religion:

  • Abraham was a polygamist (Genesis 16).
  • Jacob was a polygamist (Genesis 29).
  • Moses may have been a polygamist (Numbers 12).
  • Hundreds and thousands of reputable practitioners of ancient Christianity, including during the mortal ministry of Jesus Christ, were polygamists.
  • The law that God gave to Moses permitted polygamy, but forbade adultery and pagan marriages.

The idea that polygamy is unchristian or incompatible with Christianity or with any of the Abrahamic religions frankly denies the very Foundation of Christianity. To do so one must discredit the "father of the faithful" (Romans 4:11) and deny the covenants God made with the patriarchs and are ubiquitously affirmed in those volumes of Scripture.

Edit: Precursor bigamy legislation in the United Kingdom

There is a noteworthy law enacted in the United Kingdom, the Offences against the Person Act of 1861, that precedes the Morrill Act by one year, which states that bigamy shall be a criminal offense, together with many other criminal reforms. This is not the oldest anti-polygamy or anti-bigamy law on the books; legislation against polygamy appears to be as old as the late Roman Empire. (The Romans were actually a rare exception to the norm of polygamy in nearly all ancient cultures. Excepting times of war or the privilege of potentates, we expect monogamous marriage to be the most common form of marital union due to simple mathematics). The table on Wikipedia that you reference in your question shows the 1862 act as nearly the oldest "notable" example in modern times.

Modern Treatment of Polygamy

Fast forward to today: the State of Utah recently decriminalized adultery, fornication, and sodomy. For a long time, fornication was a misdemeanor in Utah, while polygamy was still classed as a felony. That has changed recently too, although apparently polygamy is still not treated with parity compared to extramarital relations, and perhaps never has been (enforcement of laws in the US against adultery, fornication, etc. has been a rarity). With the rapidly changing legal landscape, and questions continuing to arise about what will and will not be enforced, it is not yet clear exactly how the treatment of polygamy will compare to the treatment of sex crimes in the future. Based on the historic and present designations and enforcement rates, it appears that the old stigma is still at least somewhat in force, and polygamy may still be being treated as "more barbaric" than many forms of extramarital sexual licentiousness. The most stringent requirement advanced in Utah's state Constitution is that polygamy would be "forever prohibited"; the US Congress made it clear that this was a prerequisite to statehood (Article III, First section). As such it would seem that for the "prohibition" against polygamy to be lifted, either the US Congress would have to change its mind or Utah would have to withdraw from the union. The same is awkwardly not true of every form of sexual abuse and criminality; early Utahans noted this double standard as a way of propping up licentiousness at the expense of religious liberty. While brothels continued operating and adulterers often got off the hook, the separation of existing families was the most immediate effect of the anti-polygamy legislation.

You are correct that polygamy is victimless since it is consensual and involves as strong a vow as monogamous marriage to maintain the relationship and commitment to provide for spouse(s) and children. Extramarital sex lacks these protections for partners and children and so are far from victimless.

Footnote on comparison to incest

There is not much comparison between incest and polygamy other than their illegality. One reason why incest is scientifically wrong is the extremely high likelihood of children inheriting debilitating genetic anomalies due to inbreeding. This has been proven to be caused by parents sharing a deleterious mutation. In the days of Adam and Eve, marrying one's sibling carried practically no genetic risks because few or no genetic errors had yet accumulated. The Mosaic law forbade incest, but this cannot be used to condemn the children of Adam and Eve because Moses was ~2500 years and many generations removed from Adam and Eve, and there was sufficient genetic differentiation by that time to make the risks of inheriting a redundant defect nontrivial, hence the introduction of a new law regarding it.


In addition to the already insightful answers, the reason we need a law against polygamy is marriage has a legal status, and if a person were to be married to someone extra that would be cheating, not just in the relationship, but also legally and financially.

Now imagine opinions start changing and voters turn to favouring polygamy. In that case we would seek to decriminalize it and find a way to make marriage law apply to any number of people.

Now the problem is there are no examples anywhere of acceptable polygamy laws, that is laws allowing polygyny/andry among equals.

In the countries that have polygyny women are considered half-humans at best. Men always get custody of children after a divorce, women cannot get divorced or remarried as easily as men, women often have no property. This combined with the fact that the laws allowing only polygyny makes it a easy to write the law: marriage is one man and a number of women who have no say in anything.

  • If not having examples of laws elsewhere allowing both polygyny and polyandry, is one of the best arguments against it, then I'd say the arguments against it are extremely weak.
    – NotThatGuy
    Jul 21, 2023 at 9:38
  • I'm pretty sure your first two paragraphs are already covered by James K's answer.
    – F1Krazy
    Jul 21, 2023 at 10:36
  • Cheating in what sense? There is nothing that can be cheated in financial and dutiful obligations. "There are no examples anywhere of acceptable polygamy laws" - could you cite some historical evidence for this claim? What of people who succeeded historically in polygamous relationships, such as Abraham and Jacob? "marriage is one man and a number of women who have no say in anything." This is a non sequitur. What do women want say over? Anything except exclusive control over her husband is on the table. These same arguments might also apply to marriage in general depending on the culture.
    – pygosceles
    Jul 21, 2023 at 20:38
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    @pygosceles "What do women want say over?" Divorce, child custody, additional husbands. Also "There is nothing that can be cheated in financial and dutiful obligations": what about pensions? Mine covers my partner. If he gets an additional partner, should my pension now also cover that person? Their children? That would be a pretty big overhaul of the system.
    – Ivana
    Jul 25, 2023 at 10:34
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    Arguing specifics about a hypothetical set of polygamy rules can be interesting, but when discussing public acceptance of it, the preexisting forms of polygamy are more relevant than hypothetical. And the most widespread form of polygamy at least in the US is FLDS-style chattel woken. They have no real say in their own lives. That's not hypothetical. One could differentiate, but they'd have to be clear.
    – bharring
    Jul 25, 2023 at 16:32

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