ROUGHLY two decades ago, Antioch College in Ohio became the first in America to require students to give step-by-step consent during sexual encounters. The policy was widely mocked. “Saturday Night Live” invented an imaginary game show called “Is It Date Rape?” with a script that quoted almost verbatim from Antioch’s code. Now that code is becoming the norm at American colleges, and few people are laughing.

On September 28th Jerry Brown, California’s governor, signed a bill requiring all colleges that receive state money for student financial aid to enforce a standard of “affirmative consent”, or “yes means yes”. This means both parties must agree to sexual contact, either through verbal communication or clear, non-verbal cues. Moreover, they must do so at each stage of an encounter. An initial “yes” to a kiss doesn’t constitute a “yes” to sexual intercourse.

Silence or lack of resistance do not mean “yes”. Consent must be continual and “can be revoked at any time”. Intoxication is no defence: “It shall not be a valid excuse that the accused believed that the complainant affirmatively consented...if the accused knew or reasonably should have known that the complainant was unable to consent [because she was too drunk to] understand the fact, nature, or extent of the sexual activity.”

Sexual violence in America has declined sharply since the mid-1990s. According to the National Crime Victimisation Survey, the gold standard for measuring crimes that are often not reported, the proportion of women subjected to rape or sexual assault fell 64% between 1995 and 2005, and declined slightly further by 2010, to 1.1 per 1,000 women per year (see chart). Colleges do not appear to be more dangerous than other places where young people congregate: according to Bureau of Justice statistics, 18-24-year-olds who do and don’t attend college are about equally likely to be raped or sexually assaulted.

Nonetheless, colleges are under unprecedented pressure to make campuses safer. Activists talk of an alcohol-fuelled “rape culture”. A student at Columbia (pictured) has vowed to carry her mattress around all day until the man she says raped her is expelled. Images of what she describes as a piece of performance art, “Carry That Weight”, have landed her on the cover of New York magazine. On September 19th Barack Obama launched a campaign to prevent sexual assaults in college. This is not the first time his administration has weighed in. In 2011 the Department of Education sent colleges a letter suggesting that if they did not take steps to curb sexual violence, they could fall foul of a federal anti-discrimination law called Title IX. The letter cited an estimate that about one in five women are victims of a completed or attempted sexual assault while in college—a much higher figure than other studies find. Sceptics protest that the study in question relies on a narrow sample of students and a broad definition of sexual assault, including “any unwanted sexual contact” while the victim is incapacitated by alcohol or drugs. In the past, accusations of sexual assault were typically dealt with privately by schools, usually behind closed doors. Earlier this year Mr Obama’s administration began publishing a list of colleges and universities under investigation for violations of Title IX; it now includes more than 70, including Harvard, Princeton and Berkeley. Pushed by government and their own students, many institutions are adopting more stringent standards for dealing with sex on campus. Every member of the Ivy League except Harvard has now adopted the “affirmative consent” standard. So have many, perhaps most, other universities. Supporters of the policy say that it educates students about the nature of consent and gives them a vocabulary to use during awkward sexual encounters. “It tells students very clearly that sex without consent is sexual assault,” says Suzanne Goldberg, a law professor at Columbia University.

Critics say the approach tries to crunch human sexuality into a straitjacket. “Under this consent standard, if one partner touches his or her partner in a sexual way, and the person says ‘I am not interested tonight,’ that person has already committed sexual assault because he or she didn’t get permission upfront,” says Joe Cohn of the Foundation for Individual Rights in Education, an advocacy group. “It’s just not consistent with how adults act.”

Mr Cohn believes that a better policy would be for colleges and universities, rather than handling sexual assault complaints themselves, to refer allegations of such serious crimes directly to the police, who have had years of experience with forensic evidence. Currently many cases are heard by college disciplinary committees composed of professors, deans and students, often with no legal training. Such committees cannot jail people, of course, but they can expel them, and being labelled a rapist by a quasi-judicial body can ruin a student’s reputation for ever.

College disciplinary committees have fewer safeguards than criminal courts: often the accused has no right to a lawyer and no chance to cross-examine witnesses. The committees also tend to determine guilt based on a “preponderance of evidence” rather than “beyond a reasonable doubt”. This means that the accused can be found guilty if the panel thinks it slightly more likely than not that he is. The new “affirmative consent” law in California includes a clause requiring schools to use the “preponderance of evidence” standard.

Other states—and colleges—are likely to follow suit. “Normally the government doesn’t tell schools how to regulate student behaviour,” says Alison Johnson, a history professor at Harvard who leads a committee on sexual-assault policies. “But in the current national climate around sexual assault, if you’re not getting it done, they’re going to tell you what to do.”