This question asks why anti Polygamy laws exist.

What purpose do anti-Polygamy laws serve?


Marriage require consent of 3 parties. The man, the wife, and government.

If Ann is married to Bob, then it must be registered in government database. If Ann then want to marry Charlie, then why can't government simply make that impossible?

Before marrying anyone, government can simply says, ups, you cannot marry, you are still married based on my database.

Rather than punishing polygamy, why doesn't US government simply make that impossible by not officiating marriage between people that are not single?

Why punish something you can effectively prevent people from doing in the first place easily?

Note: This question has many good answers. I was just pointing out that I was under the impressions that polygamy can only be done by mistakes. Why would anyone commit a crime with almost 100% probability of getting caught. In game theory, it's not "reasonable" (or what's term in game theory for picking a strategy that is strictly dominated no matter what).

I think anti polygamy laws is a bit similar like https://www.news.com.au/travel/travel-updates/woman-forced-to-cancel-dream-trip-to-new-york-after-accidentally-telling-the-us-shes-a-terrorist/news-story/bc496a06a6ae8891853c0df19a06d4e1 You will be in trouble for checking yes I am a terrorist but that's pretty pointless. Why would anyone do that?

Another issue is that polyamory and sugar relationship is legal in United States. So why would anyone that want to have several woman just don't involve the state.

Hence, committing "legally recognized" polygamy, in a sense of registering your second marriage is a crime with 100% chance of getting caught and with almost nothing to gain. Doesn't seem like something need criminalizing. No body would bother doing that anyway.

Also I think this is still a legitimate question. That is why I am reopening.

  • Why downvotes? Any reason? Government can simply prevent all polygamy by not allowing polygamist to register their marriage. Why bother making a law punishing them? – user4951 Dec 10 '18 at 22:06
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    Lots of problems with this question. First, marriage isn't between the man, the wife, and the government. Marriage, as viewed by many, is between the couple and God(or in accordance to their religious traditions). This topic gets hairy, so it is sometimes beneficial to make a distinction between government marriage (civil unions) and religious marriage. IMHO, the true answer to this question lies in what the federal government actual is and what it is trying to do vs what the laws do. Government lists aren't popular among Americans. – David S Dec 10 '18 at 22:24
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    @DavidS: Marriage is a function of state government, not the federal government. – John Bode Dec 10 '18 at 22:25
  • Okay I don't really differentiate between state and federal government. In that case, why the states don't simply make polygamy impossible? It seems that if you can easily prevent something, punishing someone from doing what you can easily prevent doesn't seem like "good intention". Also I think anti polygamy laws in US punish government marriage. Am I correct there? – user4951 Dec 10 '18 at 23:09
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    How common is polygamy? How much would it cost to maintain such a database? Who would be responsible for its accuracy? How accurate would it be? At what stage during the process of marrying would it be tested against? What do you know about how marriage works in the US? What happens if someone moves to a different state? – Bryan Krause Dec 11 '18 at 0:01

If the government were to do this, it would be about as effective as the database to prevent mentally ill people from buying guns.

When [something that puts you on the list] happens in Florida, the court or government body that made the decision on the individual's mental health is required to report that record to a state law enforcement agency or the FBI.

The records would be in the National Instant Criminal Background Check System, a confidential database that houses the names and birth years of individuals ineligible to buy firearms.

A licensed gun dealer is required under federal law to run potential buyers through the criminal background check system. The process usually takes around 90 seconds, and, if all the records are in the right place, would prevent a purchaser who was previously involuntarily committed or adjudicated as mentally incompetent from getting the gun.

But federal law doesn't require states to make these mental health records part of background check system, and many fail to voluntarily report the records. And licensed gun shops aren't the only places to buy a firearm.

So having such a database would require every state to correctly submit updated records in a timely manner. If it isn't timely enough, you could get married in one state, then in another, and then the central database would have a conflict. Or you might be unable to get remarried on the day that your divorce is finalized, because the state takes three weeks to submit that paperwork.

Plus, even the firearm database, which has a clear public safety purpose (regardless of whether it achieves that purpose), has its opponents. So does the TSA No-Fly list.

From another angle, (at least in the US) there's no group who would really want to advocate for such a thing en masse. Democrats/Liberals tend to be for government oversight, but against interfering with people's personal lives. Republicans/Conservatives tend to be for smaller government, but against letting people do "immoral" things.

Finally, why should a government agency maintain a database like this without it being illegal? No government is going to want to spend money to prevent something legal from happening, without making it illegal first. And if whoever dictates that this database should be used has the power to set this restriction into it without making it officially illegal, then it's still practically illegal or the database is broken.


Thus the only thing the government can practically do is make it illegal, and punish anyone who is caught. Trying to make it technically infeasible runs into the same host of problems that current government databases have, and there's no point in creating such a database restriction for something that isn't a crime.

  • I think marital database is far simpler than mental health database. Either you're married or not. Mental health is very nuance. People used to think homosexuality as a mental disorder. – user4951 Dec 10 '18 at 23:45
  • 3 weeks paper works? Hello? One google sheet is enough and that syncs in minutes – user4951 Dec 10 '18 at 23:45
  • My marriage status is listed on my ID card and I live in Indonesia. Like government doesn't know who is married or not? I mean it's kind of easy to know if the act of marrying requires government approval – user4951 Dec 10 '18 at 23:46
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    Might be worth adding that many countries respect marriages from other countries as well; that means it's not just your country being slow with its paperwork. There's still an issue if you're married in your home country and another country, and you're going to need the whole world to agree on keeping this list. Even the countries where polygamy is legal (see the issue there?) – Erik Dec 11 '18 at 13:28
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    @user4951 In Indonesia then it would, perhaps, be possible. But in countries like the US or UK, which do not have compulsory ID cards and which shy away from them and from consolidated government records, this would be impractical. – owjburnham Dec 11 '18 at 17:25

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