But with the rise of technology, said Carissa B. Hessick, an associate professor at the Sandra Day O’Connor College of Law at Arizona State and an expert on child pornography and criminal sentencing, “now we have situations where people are being arrested and charged” in connection with digitally altered images, where no child was abused.

There remains much uncertainty about how the law should be applied in such cases, she said. But because most defendants take plea bargains instead of going to trial, the courts are often deprived of the opportunity to sort it out.

Mr. Tague argues that the state statute covers not only filming a child in a sexual activity but also making it appear that a child is engaging in that activity. But Ms. Hessick questioned whether the Michigan law could be applied in Mr. Emory’s case or “whether they’ve overcharged him.”

Even the Muskegon County sheriff, Dean Roesler, whose deputies arrested Mr. Emory after parents complained about the video, acknowledged that the case represented uncharted territory. While he found the video alarming and offensive, Sheriff Roesler said, “I realize the Internet is just a whole new arena that we’re learning to deal with in law enforcement, and actual legislation is having a hard time keeping up.”

Mr. Emory said the idea for the video arose out of planning for a Valentine’s Day variety show at a downtown club. He wrote the explicit song when he was 16, he said, and had played it in bars before. But for the variety show he wanted to pair it with “an inappropriate audience” as a comedy segment. He thought of using elderly people, he said, but decided instead on young children.