In cultures that practice marital monogamy, bigamy is the act of entering into a marriage with one person while still legally married to another. Bigamy is a crime in most western countries, and when it occurs in this context often neither the first nor second spouse is aware of the other. In countries that have bigamy laws, consent from a prior spouse makes no difference to the legality of the second marriage, which is usually considered void.
Before Christianity became the official religion of the Roman Empire, Diocletian and Maximilian passed strict anti-polygamy laws in 285 CE that mandated monogamy as the only form of legal marital relationship, as had traditionally been the case in classical Greece and Rome. In 393, the Byzantine Emperor Theodosius I issued an imperial edict to extend the ban on polygamy to Jewish communities. In 1000, Rabbi Gershom ben Judah ruled polygamy inadmissible within Jewish communities.
According to feminist historian Sarah McDougall, the Christian European insistence on monogamy and its enforcement arose as a consequence of 16th Century Islamic incursions into Central Europe and the advent of European colonialism within the Americas, Africa and Asia, which exposed European Christians to cultures that practised polygamy. As a consequence, nominal Christian male bigamists were subjected to unprecedented harsh punishments, such as execution, galley servitude, exile, and prolonged imprisonment. McDougall argues that female bigamists were not as harshly punished due to women's perceived inferiority and absence of moral agency.
Most western countries do not recognize polygamous marriages, and consider bigamy a crime. Several countries also prohibit people from living a polygamous lifestyle. This is the case in some states of the United States where the criminalization of a polygamous lifestyle originated as anti-Mormon laws, although they are rarely enforced.
In diplomatic law, consular spouses from polygamous countries are sometimes exempt from a general prohibition on polygamy in host countries. In some such countries, only one spouse of a polygamous diplomat may be accredited, however.
China: Illegal (but tolerated for some minorities, such as Tibetans, in some rural areas in the South West) .
Colombia Illegal with exceptions (such as religion). Although bigamy no longer exists as a lone figure in the Colombian judicial code marrying someone new without dissolving an earlier marriage may yield to other felonies such as civil status forgery or suppression of information.
Republic of Ireland: Bigamy is a statutory offence. It is committed by a person who, being married to another person, goes through a ceremony capable of producing a valid marriage with a third person. The offence is created by section 57 of the Offences against the Person Act 1861. This section replaces section 26 of the Act 10 Geo. 4 c. 34 for the Republic of Ireland.
Malaysia: Permitted for Muslims; required to obtain judicial consent, show financial capability, and several strict conditions. Some variation in law between states (family law relating to non-Muslims is under federal jurisdiction).
In the United Kingdom a person guilty of bigamy is liable, on conviction on indictment, to imprisonment for a term not exceeding seven years, or on summary conviction to imprisonment for a term not exceeding six months, or to a fine not exceeding the prescribed sum, or to both.
In the United States, the Model Penal Code (section 230.1) defines bigamy as a misdemeanor and polygamy as a felony. Having more than one spouse at the same time gets classified as polygamy, and bumped to a felony, if it is done "in purported exercise of a plural marriage..." According to Joel Feinberg in Moral Limits of the Criminal Law: "Righteously, flaunting one's illicit relationships, according to the Code, is apparently a morally aggravating circumstance, more punishable than its clandestine and deceptive counterpart."