It’s 2016, but you wouldn’t have known it by looking at the headlines coming out of Virginia.

In Richmond, the state senate killed a bill on Jan. 18 that would have decriminalized adultery. Virginia is one of 21 states that retains criminal prohibitions on marital infidelity—a statute that’s far out of touch with social realities. Between 19 and 23 percent of men and 14 to 19 percent of women report committing adultery; experts say the actual numbers are far greater. Few individuals are prosecuted for these crimes, and, in the circumstances in which they are, argue strongly for repeal.

Consider John Bushey. In 2004, the 66-year-old lawyer for the west of the Beltway town of Luray pleaded guilty to adultery and lost his job as a consequence. After his extramarital affair ended badly, the woman involved went to the police. An assistant commonwealth attorney later defended the decision to prosecute: “We’re not out beating bushes and certainly we’re not peeking in windows. However, in this case, it was thrown in our face.” Initially, it looked like Bushey might challenge the law; instead, he ended up accepting a deal that required 20 hours of community service in exchange for having the charges dropped and his record cleared.

Bushey is an isolated case. But others could arise in the 21 states that still have misdemeanor or felony prohibitions on adultery. It also figures as a basis for job terminations, sanctions, or demotions (particularly in the military), and as a factor in allocating property and custody in divorce cases. An overhaul of these laws is long overdue. Enforcement of criminal prohibitions has been infrequent, intrusive, idiosyncratic, and ineffectual. It should be unconstitutional. In employment cases, courts should not permit dismissals based on private sexual conduct absent some demonstrated impairment of job performance. Nor should courts allow infidelity to influence alimony and custody awards.

None of these reforms should be seen as diminishing societal respect for marriage as an institution. Rather, it simply recognizes the limits of the law in policing fidelity—and the excessive costs of attempting to do so.

Criminal prosecutions are rare, but should be rarer still, given their arbitrary nature. In some jurisdictions, an aggrieved individual can file a complaint to request a prosecution against an estranged spouse. An example is Dave Banks’s 2010 complaint that his wife of 17 years had cheated on him. As Banks explained to a national news network reporter, “If they used… [the adultery statute] all the time, maybe women or men would think twice about going and jumping in the sack and throwing away their marriage.”

But in the absence of such implausibly draconian enforcement efforts, the deterrence value of criminal prohibitions seems minimal. The widespread public ignorance about such statutes was well illustrated in 2008, when New York Gov. David Paterson acknowledged at news conference that he’d had several extramarital relationships but “didn’t break the law.” The New York Times followed up with a report that began “Well, actually…” Adultery is a misdemeanor in New York, punishable by a fine of $500 or 90 days in jail.

Such prohibitions should be repealed, or held unconstitutional. As the Supreme Court recognized when striking down a criminal sodomy statute in Lawrence v. Texas, the Constitution reflects “an emerging awareness” of “substantial protection to adult persons in deciding how to conduct their private lives in matters pertaining to sex.” Although the state has an interest in fostering marriage, the frequency with which adultery occurs, and the infrequency with which adultery statutes are enforced, suggest that criminal prohibitions are an ineffective means of shoring up marital relationships.

So too, adultery should cease to figure in other contexts. In family-law cases, marital infidelity bears no necessary relationship to parental fitness for custody, and it is far less relevant in financial determinations than factors such as spousal need. Nor does adultery demonstrate unfitness for public employment or justify work-related sanctions and military discipline. A case in point involves a 2008 Utah police department’s reprimand of a married police officer who had sex while she was at an out-of-town training seminar. In a federal court’s view, maintaining public respect was a sufficient justification for the sanction. Such vague invocations of community disapproval should not be an adequate basis for intrusive disciplinary processes. If off-duty conduct does not pose a demonstrable threat to the functioning of the workplace, employees’ private sexual activities should remain private. Lt. Kelly Flynn, the nation’s first female B-52 bomber pilot, should not have lost that job for charges stemming from adultery.

That view is widely shared. In public polling, more than half of Americans surveyed said that military rules on adultery should be changed. And although over 90 percent of Americans say they think adultery is wrong, between two-thirds and three-quarters agree that it should not be a crime. Courts and legislatures should catch up. Virginia sets the wrong example.

Deborah L. Rhode is the author of Adultery: Infidelity and the Law (Harvard Press)