Students walk across the University of Minnesota Twin Cities campus on Monday, Oct. 24, 2011. Tim Post / MPR News 2011

"No means no" might not cut it anymore at the University of Minnesota.

Student leaders are looking into a potential rule that would require their peers to give some form of "yes" before having sex. Supporters say an "affirmative consent" policy could make it easier to determine in sexual assault cases whether acts were truly consensual and remake campus attitudes about sexual behavior.

"It's fundamentally shifting how we think about sexual assault, and that itself is a pretty big hurdle to overcome," said student body president Joelle Stangler, who's pushing for a study of the matter.

Stangler says she's not sure yet if such a policy is right for the University of Minnesota, but wants to explore it. The student government recently called for a panel to examine the merits of changing the policy and Stangler hopes recommendations could come by the end of spring semester.

University leaders say the U already has a strong policy, but vice provost Danita Brown Young said she's open to working with students to review it and make any necessary improvements.

The university's current student conduct policy requires getting the consent of another to engage in a sexual act. Consent isn't valid if obtained through force or intimidation or if a student is unconscious, drunk or high on drugs. Besides facing criminal charges, a student found guilty of sexual assault could be expelled.

Still, what actually constitutes consent at the university is unclear to some. The university's current policy says it must be "mutually understood," which Stangler called an "incredibly vague" standard. When two students are in the heat of the moment, she said, "there's a lot of assumption going on" about what each person wants.

Letting things progress until someone says "no" doesn't really work, said Katie Eichele, director of the university's Aurora Center, which offers support services for victims of sexual assault and domestic violence.

By the time the "no" is given, she said, "it might actually be too late. You might actually be engaging in behavior that someone was really uncomfortable (with) to begin with."

And just because some people don't say "no" during a sexual encounter doesn't mean they're willing to have sex. Eichele said more than 40 percent of sexual-assault victims freeze up in a trauma-induced paralysis that prevents them from saying "no."

In contrast, requiring some sort of "yes" would make it easier for two people to understand the limits in sexual encounters, supporters of a policy say. And it would make it easier for investigators to determine whether a sexual act was indeed consensual.

Asking for sex doesn't need to be awkward, Stangler she added. "Someone might be able to ask, 'Are you comfortable going further?' or 'Do you want to keep going?' or 'Can we keep going?' It's a one-sentence sort of thing."

Antioch College in Ohio drew sneers in 1991 when it became the first campus to issue an explicit affirmative consent rule. Critics thought it ridiculous that students had to ask for permission to go to the next stage of a sexual encounter.

Almost a quarter century later, no one's laughing. Last fall, California became the first state to require the policy at all of its campuses. At least three Minnesota colleges — the University of St. Thomas, Carleton College and Augsburg College — have similar policies.

Some students at the U said getting a "yes" was a good idea, and not necessarily awkward. Several women said being asked for permission was flattering. Not asking permission is "really disrespectful," said Lauren Witte, a senior psychology major from Luverne.

Senior Kevin McCollow, left, talks with two University of Minnesota classmates on Jan. 6, 2015, about a potential new affirmative-consent policy. Alex Friedrich / MPR News

Men said they'd have no real problem asking. But Kevin McCollow, a computer science senior from Lino Lakes, said having to ask permission at various stages "would be a buzzkill. You'd be in the mood, in the zone, and you say, 'Pause everything. Let me wait until you answer and say yes.' I think she would be thrown off, and you would be thrown off at that point, and everybody would just feel awkward, probably," he said, adding, "But maybe it's for the best."

George Washington University law professor John Banzhaf, a critic of affirmative consent, says even asking someone for consent is fraught with ambiguity.

"Suppose the guy says, 'May I touch your breast?' She says, 'Yes.' OK, does that mean through her shirt?" he said. "Does it mean taking off her shirt through her bra? Does it mean reaching under the bra, but not taking it off?"

Those considering a policy at the U also haven't worked out yet at which stages a student at the U would have to ask for consent during a sexual encounter. Banzhaf said making a request at every new stage would be "incompatible" with human nature.

Also unclear is just how a student would answer "yes."

The clearest form would be a spoken "yes," or "sure," or "OK," but Eichele says that's not "not how our students operate all the time" and that a person could give consent with a nod of the head, by taking off their own clothes, or guiding a partner's hands.

She acknowledged that such gestures are trickier to interpret than words, and said those considering a new policy "would have to carefully scrutinize" what's considered a gesture of consent.