But adultery may soon be legal in the Empire State thanks to a bill working its way through the New York Legislature, which would finally repeal the seldom-used law that is punishable by up to three months behind bars.

Adultery bans are still on the books in several states across the US, though charges are also rare and convictions even rarer. They were traditionally enacted to reduce the number of divorces at a time when a cheating spouse was the only way to secure a legal split.

Adultery, a misdemeanor in New York since 1907, is defined in state code as when a person “engages in sexual intercourse with another person at a time when he has a living spouse, or the other person has a living spouse”.

Just a few weeks after it went into effect, a married man and a 25-year-old woman were the first people arrested under the new law after the man's wife sued for divorce, according to a New York Times article from the time.

Only about a dozen people have been charged under New York's law since 1972, and of those, just five cases have netted convictions, according to Assemblyman Charles Lavine, who sponsored the bill to appeal the ban. The last adultery charge in New York appears to have been filed in 2010 against a woman who was caught engaging in a sex act in a public park, but it was later dropped as part of a plea deal.

Lavine says it's time to throw out the law given that it's never enforced and because prosecutors shouldn't be digging into what willing adults do behind closed doors.

“It just makes no sense whatsoever and we've come a long way since intimate relationships between consenting adults are considered immoral,” he said. “It's a joke. This law was someone's expression of moral outrage.”

Katharine B. Silbaugh, a law professor at Boston University who co-authored “A Guide to America's Sex Laws”, said adultery bans were punitive measures aimed at women, intended to discourage extramarital affairs that could throw a child's parentage into question.

“Let's just say this: patriarchy,” Silbaugh said. New York's bill to repeal its ban has already passed the Assembly and is expected to soon pass the Senate before it can move to the governor's office for a signature.

The law almost was removed from the books in the 1960s after a state commission tasked with updating the entire penal code found the ban practically impossible to enforce. The commission's leader was quoted at the time as saying, “this is a matter of private morality, not of law".

The panel's changes were initially accepted in the Assembly, but the chamber restored the adultery law after a politician argued its elimination might appear like the state was endorsing infidelity, according to a 1965 New York Times article.

Another Times article from the period also detailed pushback from at least one religious group that argued adultery undermined marriages and the common good. The penal code changes were eventually signed into law, with the adultery ban intact.

Most states that still have adultery laws classify them as misdemeanors, but Oklahoma, Wisconsin and Michigan treat adultery as felony offenses. Several states, including Colorado and New Hampshire have moved to repeal their adultery laws, using similar arguments as Assemblyman Lavine.

There also are lingering questions over whether adultery bans are even constitutional.

A 2003 Supreme Court decision that struck down sodomy laws cast doubt on whether adultery laws could pass muster, with then-Justice Antonin Scalia writing in his dissent that the court's ruling put the bans in question.

However, in the court's landmark 2022 decision that stripped away abortion protections, Justice Clarence Thomas wrote that the Supreme Court “ should reconsider ” its sodomy law decision, as well as its decision legalizing same-sex marriage, in light of its newer interpretation of Constitutional protections around liberty and privacy.

The high court's hypothetical stance on adultery laws might be mostly academic fodder given how rare it is for such a charge to be filed.