South Korea's constitutional court ruled on Feb 26 that having an extramarital affair was not a crime, striking out a 62-year-old law that put adulterers in jail for up to two years.
"It should be left to the free will and love of people to decide whether to maintain marriage, and the matter should not be externally forced through a criminal code," five of the court's nine justices said in a joint statement.
Surprisingly, there are quite a few cities where such a law remains in the books, including dozens of states in the United States. But in many places, prosecutions are rare even if the laws have not been reviewed.
In Asia, a notable example is Taiwan, where the constitutionality of the law has also been questioned.
In 2013, the debate was rekindled when a Taiwanese widow faced the theoretical possibility of 298 years in jail for an affair with a married man. Under Taiwanese law, each offence was worth up to four months in jail, and the couple confessed to more than 800 trysts over five years. The man, 50, avoided legal punishment after his wife, who had filed the complaint against the duo, decided to forgive him and drop the lawsuit against him.
The Philippines also penalises adultery, where the punishment can be a jail sentence of up to seven years. The law differentiates between men and women, and for men, the offence is termed "concubinage". It is rarely enforced in the largely Roman Catholic country.
In India, it is a crime for a man to have sexual relations with a married woman, but there are no laws against adultery for women. The offence originated because the woman is treated as the husband's property, according to the Times of India.
In the United States, about 20 states still criminalise adultery as laws from the 1800s persist. Some states, like New Hampshire in 2013, only repealed their laws against infidelity in recent years.
In New York, it is still a "Class B misdemeanor", which is in the same category as criminal trespass, and prostitution. A sentence of up to a year can be imposed for such offences.
In Muslim countries where Syariah law is adhered to, such as Saudi Arabia, Dubai and Iran, adultery is a crime and punishable by jail terms or death. In Pakistan, adultery is punishable by death by stoning under the Zina and Hudud Act of 1979. In Indonesia's Aceh province, a law stipulates punishments of up to 100 lashes of the cane for unmarried people who commit adultery and death by stoning for married people. It was enacted in 2009, overturned, then passed again late last year.