Not too long ago, the term “marital rape” was considered an oxymoron. In some U.S. states, it might as well still be one.

Lawmakers in Ohio are trying to remove archaic forms of “marital privilege” in state laws pertaining to rape, The Columbus Dispatch reports. Although marital rape is illegal in Ohio as well as nationwide, the notion of marital privilege or exemption dates from an era when a man could only be charged with rape if the alleged victim was not his wife—an era that only ended in the United States on July 5, 1993 when North Carolina criminalized marital rape, becoming the final state to do so.

But although marital rape is illegal in the United States, Ohio is one of several states in which marital rape continues to be handled in a substantially different way than rape outside of marriage, whether it is charged under a different section of criminal code, restricted to a shorter reporting period, held to a different standard of coercion and force, or given a different punishment. Together, these double standards make marital rape—an already “infrequently prosecuted” crime according to the Rape, Abuse, and Incest National Network (RAINN)—even more challenging to prosecute.

As of April 2014, according to an AEquitas report, eight states still had marital rape exemptions for some offenses, not including the states without exemptions that simply prosecute marital rape differently.

Ohio state law, for example, contains two distinct subsections for rape, one of which applies only to “sexual conduct” with someone who is “not the spouse of the offender” or a separated spouse. This section applies to situations in which the offender uses a “drug, intoxicant, or controlled substance” to lessen the victim’s resistance and cases in which the victim has a “mental or physical condition” that prevents consent. But this section does not apply to sexual conduct between cohabitating spouses, in which case there must be “force or threat of force”—not just coercion—for rape legislation to even apply in the first place.

In essence, as one Ohio local paper put it in a recent staff editorial: “In Ohio, a woman can be drugged and sexually assaulted—legally—if the perpetrator is her spouse.” And although the vast majority of marital rape cases involve a female victim and male offender, this would technically apply to a spouse of any gender.

Oklahoma, which became the penultimate state to criminalize marital rape in 1993, has similar rape legislation requiring “force or violence” if the victim is the “spouse of the perpetrator” and covering the coercive use of narcotics and anesthetics in cases where the victim is not the spouse. The legislation also deems penetration to be rape in instances when “the victim is at the time unconscious,” so long as that victim is not the perpetrator’s spouse. In other words, an Oklahoma resident can penetrate not just a drugged but also a sleeping spouse without the act legally qualifying as rape.

Earlier this year, a British woman named Sarah Tetley discovered that she had been raped over 300 times in her sleep by her own husband who fastidiously documented his assaults on video. Her husband was sentenced to 12 years in prison but if the Tetleys had lived in Oklahoma, that sentence may have been considerably more difficult to obtain.

Many of the other states that differentiate between rape and marital rape do so through language similar to Ohio’s “force or threat of force” requirement but South Carolina state code goes so far as to require “the threat of use of a weapon” and/or “physical violence of a high and aggravated nature” in order to prosecute what it terms “spousal sexual battery.”

By comparison, South Carolina only requires “force or coercion,” “aggravated coercion,” and, at most, “aggravated force” to prosecute various degrees of “criminal sexual misconduct” when the victim is either not a spouse or a separated spouse—no mention of weapons and no requirement of elevated level of violence.

By treating marital rape as a separate crime from other forms of rape, these states continue to lend credence to the centuries-old idea that consent is more difficult to define within the bounds of marriage. That particular notion dates back “hundreds of years,” as RAINN notes, to 17th-century British common law, in which a woman’s unconditional sexual consent was considered to be part of the marriage contract.

This understanding of marriage law persisted in the U.S. until second-wave feminists drew attention to marital rape and other forms of spousal abuse in the 1970s. In 1978, for example, Laura X—who adopted that surname as a nod to Malcolm X—founded the now-defunct National Clearinghouse on Marital and Date Rape (NCMDR), a research center that drew media attention to the concept of marital rape and participated in several state campaigns to criminalize marital rape through the 1980s. These campaigns reached a tipping point in the early 1990s when the majority of states had criminalized marital rape.

At the time, little was known about the extent of marital rape but the NCMDR along with independent researchers like Diana Russell also began to collect data on its frequency. Marital rape is still an understudied topic but estimates from that early period suggest that anywhere between 10 to 34 percent of women have been raped or sexually assaulted by a spouse or intimate partner. The Center for Disease Control (CDC) estimates that more than half of female rape victims report being raped by an intimate partner.

It remains difficult, however, to know precisely how commonplace marital rape is specifically because it is “the most underreported category of sexual assault,” according to the Encyclopedia of Victimology and Crime Prevention, despite its fairly recent criminalization. Nearly 70 percent of rapes go unreported—a percentage that is likely much higher for marital rapes alone.

As RAINN’s resources suggest, victims of marital rape often feel pressured to preserve their marriages and they may not be able to come to terms with the understanding that their spouses are “rapists”—both factors that contribute to the reduced profile of marital rape relative to other, more widely publicized forms of sexual assault.

Several women who discover that their husbands had non-consensual sex with them while they were sleeping, for example, go to online message boards or write to advice columnists to solicit opinions about whether or not the act qualified as rape. On one message board, an anonymous woman describes having woken up finding her pants ripped off and semen on her genitals after she had already explicitly asked her husband to stop this behavior.

“Am I making a big deal out of nothing?” she asks.

The persistence of these questions demonstrate that misconceptions about the legitimacy of marital rape on a cultural level are alive and well in the U.S. even though the act itself has been criminalized in all 50 states. Last week, one Christian blogger penned a controversial post claiming that “[b]iblically speaking, there is no such thing as ‘marital rape,” citing scriptures such as 1 Corinthians 7:4, which states: “The wife does not have authority over her own body but yields it to her husband.”

He downplays the idea that “if a man has sex with his wife when she is not [in] the mood [then] this is rape” and proceeds to advise Christian husbands that “if she yields (even grudgingly), you ought to take it.” For the many states like Ohio that have yet to update their marital rape legislation for the 21st century, this biblical advice is eerily close to being the law of the land.

Special state laws for marital rape exist across the U.S. in states as liberal as Connecticut, which requires the familiar “use of force” or the “threat of the use of force” to prosecute, and as conservative as Idaho, where “[n]o person shall be convicted of rape for any act or acts with that person’s spouse” unless the spouse resisted but was “overcome by force or violence,” was threatened with violence, or drugged.

Marital rape is illegal everywhere in the U.S. but the cultural and legal obstacles facing its victims remain formidable. Ohio may be revisiting its rape legislation soon but a sizable fraction of state legislatures still seem caught in a painfully recent past.