The blood is still drying on Clay McCann's hands when he walks into a remote ranger station, slides a warm gun across the desk, and informs the ranger that he's just killed four campers.

"Do you want me to call a lawyer?" the alarmed ranger asks.

"I am a lawyer," McCann says.

So begins C. J. Box's 2007 thriller Free Fire, the seventh in a book series about a Wyoming game warden. The novel's plot spins on the premise that in an uninhabited, 50-square-mile portion of Yellowstone National Park, you can legally get away with murder.

The book's premise originates from a 14-page article called "The Perfect Crime" by Michigan State University law professor Brian Kalt. The article describes a judicial no-man's land in the Idaho part of Yellowstone, where a person can commit a crime and get off scot-free due to sloppy jurisdictional boundaries.

In 2004, Kalt was weeks away from becoming a father. Before the baby arrived, he wanted to churn out one last article to stay on track for tenure. He was researching obscure jurisdictional gray areas when he found a reference to the unusual jurisdiction of Yellowstone National Park. Like all national parks, Yellowstone is federal land. Portions of it fall in Idaho, Montana, and Wyoming, but Congress placed the entire park in Wyoming's federal district. It's the only federal court district in the country that crosses state lines.

Such trivia would scarcely summon a yawn from a layperson, but to a constitutional lawyer like Kalt, it was a flapping red flag. Kalt knew that Article III of the Constitution requires federal criminal trials to be held in the state in which the crime was committed. And the Sixth Amendment entitles a federal criminal defendant to a trial by jurors living in the state and district where the crime was committed. But if someone committed a crime in the uninhabited Idaho portion of Yellowstone, Kalt surmised, it would be impossible to form a jury. And being federal land, the state would have no jurisdiction. Here was a clear constitutional provision enabling criminal immunity in 50 square miles of America's oldest national park.

"The more I dug into it, the more interested I got," Kalt told me recently when I called him at his office in East Lansing. "People have this fascination with uncovering a loophole for the perfect crime. There are a lot of different approaches to it. But in terms of geography, there's just this one spot."

Kalt cranked out the paper in two weeks—before his wife gave birth—and the Georgetown Law Journal agreed to publish it in 2005. But Kalt worried his paper might inspire someone to schedule a trip to Yellowstone with the person they liked least. So before it came out, he sent copies to the Department of Justice, the US attorney in Wyoming, and the House and Senate judiciary committees. He hoped they would close the loophole before he broadcasted it to the world. It would be a simple fix, Kalt wrote, for Congress to divide Yellowstone into three federal districts—the Idaho portion going to Idaho, the Montana portion to Montana, and the Wyoming portion to Wyoming. He even drafted the legislation language. It was three lines long.

But Kalt barely got a response. From what he did hear, it seemed no one intended to do a thing. "I naïvely thought that once Congress found out about this, they'd think it was a problem worth fixing and they'd fix it," he told me. "But nothing happens in Washington just because it's a good idea."

"People have this fascination with uncovering a loophole for the perfect crime. In terms of geography, there's just this one spot." — Brian Kalt

When the paper was published, the media went nuts. Stories appeared in the Washington Post, the BBC, NPR, and even a Japanese newspaper. Wyoming-based crime writer C. J. Box read about it and thought it would make a great plot for a novel.

"I write about mystery, suspense, and crime, so the idea of a perfect crime anywhere, and especially in my neighborhood, was just really intriguing," Box told me over the phone.

His novel, Free Fire, made the New York Times extended best-seller list and continues to be popular. "Every time I go on tour, someone asks me about it," Box said. "The book is sold all over Yellowstone, which I find really interesting. People are still buying it like crazy."

Kalt notes in his article that even in the Zone of Death it would be difficult to get away with a crime completely. First, the crime would have to be serious enough to entitle the defendant to a jury trial, since lesser offenses could lead to fines or even short prison sentences. The crime would need to happen entirely within the park. (If it were orchestrated elsewhere, the defendant could be charged with something like "conspiracy to commit murder" in another district.) And even then, the defendant could still face civil lawsuits, like getting sued by a victim's next of kin. Finally, there aren't many opportunities for crime in an area that is uninhabited, and remote—there's not even a road connecting it to the rest of Yellowstone.

"All of these things reduce the incentive," Kalt admits. "It becomes harder to imagine someone relying on my theory and getting away with it."

Even still, Kalt is worried about the wait-and-see approach that Congress is taking to this loophole. "I'm less concerned about the odds than the stakes," he told me. "I don't think something is likely to happen, but it would be really bad if it did. If Congress really wanted to fix this, it wouldn't take long at all. The problem isn't that it's complicated; it's that they're not interested in it."

Congress doesn't seem to agree. Wyoming senator Michael Enzi's press secretary told me in an emailed statement that "Senator Enzi has studied the 'zone of death' issue in Yellowstone National Park, and there does not seem to be a simple legislative fix." Idaho senator Jim Risch told me the argument is "science fiction" and insists the state of Idaho would have jurisdiction over a crime there. "This is all very romantic and a great fictional thing," he said, "but I'm telling you, the states have jurisdiction." (This statute, however, clearly places Yellowstone under the "sole and exclusive jurisdiction of the United States.")

Kalt, for his part, isn't surprised that lawmakers are sitting on their hands. "They don't deal with hypothetical threats," he said. "They deal with concerns that are currently affecting influential constituents."

Still, the inaction has caused him some existential handwringing. "The question I usually get is, 'Why write the article?'" he told me. "If you know they're not going to fix it, why bring it up?' I don't really have a good answer, other than to say I'm optimistic and that maybe, every once in awhile, something happens."

Until then, Kalt's theory of the perfect crime needs only the perfect criminal to walk into the woods and test it. Then the answer will be settled once and for all. Unfortunately, someone may have to die first. And that's not an outlandish notion in America's national parks—in 2015 a man was stabbed to death in Great Smoky Mountains National Park, and in 2013, a woman pushed her newlywed husband over a cliff in Glacier National Park.

When Free Fire came out, the publisher brought Kalt to Wyoming to speak at some publicity events. After one talk, someone suggested they drive out to the Idaho portion of the park to take some pictures. It's a beautiful area, by all accounts—an untrampled wilderness of lodgepole pines, grizzly bears, and waterfalls. But Kalt had no interest in tempting fate.

"I'm not going there for a million dollars," he said. "Not until this is fixed and probably not even then. The irony gods would have a field day with that one."