California has become the first state in the US to adopt a "yes means yes" law for universities requiring students to obtain overt agreement to sex.
The "affirmative consent" measure was signed into law by Governor Jerry Brown as politicians across the country seek ways to curb what has been described as an epidemic of rape and other sexual assaults on college campuses.
The law, called SB967, applies to all post secondary school institutions which receive state funds for student financial aid.
Under the legislation, students will not be considered to have consented to sex if they remain silent or fail to resist. Those incapacitated by alcohol or drugs, or who are unconscious or asleep, are assumed to be incapable of giving their agreement to sexual activity.
But consent may be non-verbal, such as through giving a nod of the head or moving closer to the other person.
Statistics show that one in four female students will be assaulted during her four years at an American university, yet less than a third of those found to have carried out an attack are expelled. The White House has threatened to withdraw funding from colleges which they accuse of failing to handle complaints in an appropriate manner.
Elite Ivy League institutions including Harvard and New York's Columbia University are among those being sued by alleged victims who say the authorities failed to punish their attackers adequately.
In California, this summer's graduating class at Stanford, one of the top universities in the country, put red tape on their mortar boards as part of an ongoing protest against the bureaucracy they claimed prevented the university from expelling a man found to have raped a fellow student.
College rapes and sexual assaults are notoriously difficult to prosecute as they often involve alcohol and claims by the perpetrator that the victim consented. Los Angeles Senator Kevin de Leon, who drew up the "yes means yes" law, said it would transform the way campuses prevented and investigated sexual assaults.
The law also includes new requirements for steps university authorities must take when they receive a complaint against a student, including offering victims counselling and barring inappropriate questioning.
Mr De Leon said: "Every student deserves a learning environment that is safe and healthy. "The State of California will not allow [colleges] to sweep rape cases under the rug. We've shifted the conversation regarding sexual assault to one of prevention, justice, and healing."
(© Daily Telegraph London)