About 20 states have laws that can make it difficult to prosecute sexual assault cases if accusers voluntarily drank or took drugs. As detailed allegations of a 2024 gang rape at Cornell University emerged last month, Summer Willis felt both horror and a sense of recognition. There were fraternity brothers exchanging vulgar messages about the accuser on Snapchat, echoing what Willis says happened after she herself was assaulted in 2014. And there was a district attorney saying on television that state law had made filing charges difficult or impossible, just as Willis had been told years ago. “I almost threw...