“Gender fraud” — when people misrepresent their birth gender to potential sexual mates — likewise remains a gray area. Sean O’Neill was convicted of gender fraud in Colorado in 1996, and five people have been convicted in the United Kingdom since 2012.

While there are laws to protect against “catfishing,” or online impersonation, they typically focus on identity theft for financial gain or fraud, said Brad Shear, a lawyer in Bethesda, Md., who specializes in sexual privacy and cybersecurity law.

But what happens when there’s no financial gain? That depends on where you live. In some states, “If you pretend to be a particular person such as Tom Brady and the other person is relying on that claim to consent to sex, that may be deemed a sexual assault,” said Mr. Shear.

In Iowa in April 2015, Michael Kelso-Christy, who was 23 at the time, created a fake Facebook account under the name of a man who had attended his high school. He messaged several women under this name, and one woman actually met him at her home, where she was waiting for him blindfolded, per his request. They had sex, and he left. Soon after, his Facebook account disappeared and he stopped messaging her. That’s when the woman realized he was an impostor, and called the police.

After an appeal by Mr. Kelso-Christy, Chief Justice Mark Cady ultimately ruled in the woman’s favor, noting that Mr. Kelso-Christy had denied her the “‘freedom of choice’ that breathes life into our sexual abuse statutes.” He was sentenced to 10 years in prison.

But the law remains fuzzy in many locales.

Some worry that legislating deception is a slippery slope, because where do you draw the line? Is it deception if a woman dates two men concurrently and they don’t know about each other? Or what if you inject Botox into your crow’s feet and say you are younger than you are, or say “I love you” in order to have sex, but don’t mean it? In 2014, a sexual assault by fraud bill was introduced in New Jersey after a woman was impregnated by a man who falsely claimed to be a British spy. The bill went nowhere.

In February 2018, Donald Ward was acquitted in the Indiana case and his record expunged. Kirk Freeman, his lawyer, argued that lying and deceit didn’t count as rape. In January of this year, legislators introduced two bills that added a definition of deception to Indiana’s rape law, and also defined any sexual activity as rape if there was no consent. Neither bill was heard.