In the early hours of April 1, neither student at the University of Southern California knew what the other had had to drink. An Uber was called, and the male student was seen on video following the female student into her dorm, where they had sex.

The woman later told the police she did not remember the encounter, and in May, prosecutors charged the male student, Armaan Premjee, 20, with rape. But a California judge dismissed the case last week after reviewing security video from the Banditos nightclub in Los Angeles and the woman’s dorm.

The videos showed the woman leading Mr. Premjee from the club, taking his photograph, following him into an Uber and, at her dorm, swiping an access card and allowing him inside.

The judge said during a preliminary hearing last week that he believed that the sex was consensual and that the videos were a “very strong indication” the woman was the initiator, according to reports.

[Video: Security footage from nightclub clears USC student of rape” Watch on YouTube.]

Security footage from nightclub clears USC student of rape”
Video by Graham Kenneth

In an interview, Mr. Premjee said: “Without evidence, there’s no way to prove that consent did happen or didn’t happen. It’s just one person’s word against another.”

In 2014, California became the first state to require university students to receive “active consent” before all sexual activity. The outcome of the case pits the state law against the university’s policy.

U.S.C.’s rules state that a person who is intoxicated is “not capable of giving valid, affirmative consent.” A student misconduct investigation involving Mr. Premjee within the university’s Title IX office remains active. If found responsible, Mr. Premjee, a junior studying business administration, could be expelled. The female student has not been identified, which is routine in cases involving claims of sexual assault.

“Affirmative” or “active” consent varies across states, but it typically requires a verbal or nonverbal “yes” from both parties. Under President Barack Obama, universities used Title IX, the 1972 law requiring universities to protect students from rape and sexual assault, to investigate allegations involving their students.

In 2014, Gov. Andrew M. Cuomo of New York was quick to follow California, ordering the State University of New York to overhaul its sexual assault policies and make affirmative consent mandatory on all 64 campuses. SUNY obliged, but three years later, an appeals court reversed a decision by SUNY Potsdam to expel a student for sexual assault. The court claimed that the university’s investigation had been based on hearsay.

In 2015, Indiana University, which defines consent as something that requires sobriety, found that a male student had sexually assaulted a female student who had been drinking. The case was investigated by the university’s Title IX office, and the male student was expelled, but in 2016 prosecutors dismissed the case in criminal court, citing insufficient evidence.

Many universities, from public state colleges to the Ivy Leagues, have come under fire for how they have dealt with sexual assault investigations. The Chronicle of Higher Education has tracked the federal government’s investigations of colleges’ possible mishandling of sexual assault reports. As of Saturday, there were 419 such investigations, of which 350 remained open.

In early July, the education secretary, Betsy DeVos, said she intended to take a hard look at whether the Obama administration’s campus rape policies, which jump-started the “affirmative” and “active” consent movement, deprived accused students of their rights.

In an interview with The New York Times, the official appointed to lead the Office of Civil Rights, Candice E. Jackson, said that “90 percent” of sexual assault accusations on campus “fall into the category of ‘we were both drunk,’ ‘we broke up, and six months later I found myself under a Title IX investigation because she just decided that our last sleeping together was not quite right.’” Ms. Jackson later apologized, calling her remarks “flippant.”

Critics of Ms. DeVos say that the Obama-era policies had a positive effect on women on college campuses. Brett Sokolow, the executive director of the Association of Title IX Administrators, says he is playing a “long game.”

“Title IX is 45 years old,” he said. “It’s waxed and waned. It isn’t going anywhere. We just have to figure out how to navigate it.”

In February, End Rape on Campus, a survivor advocacy organization, created the hashtag #DearBetsy, a reference to the education secretary, and urged the posting of messages on Twitter in support of “sexual assault survivors.”

In the past few weeks, Twitter users on all sides of the heated debate began using the hashtag:

Mr. Premjee said on Saturday that he was not aware of the national debate or of Ms. DeVos’s position on the issue, but added that it sounded like one he would support.

“The key issue here is evidence,” he said. “In most sexual assault cases, there’s not video evidence like there was in my case. Innocent men are put in prison for that, or are punished, or kicked out of school.”