This is the fact from which the storyline originates:
The United States District Court for the District of Wyoming is currently the only United States district court to have jurisdiction over parts of multiple states. This is because its jurisdiction includes all of Yellowstone National Park, which extends slightly beyond Wyoming's boundaries into Idaho and Montana. In addition, the federal government has exclusive jurisdiction over the park, so crimes committed in the park cannot be prosecuted under any of the states' laws.
Trials in the district court are normally held at the federal courthouse in Cheyenne, Wyoming. However, the Sixth Amendment to the United States Constitution decrees that juries in federal criminal cases must be made up of citizens who are from both the district and state where the crime was committed. Because of this, charges for a crime alleged to have been committed in the area of the park in Idaho would have to be tried before a jury consisting entirely of residents of that area, and the trial would also have to take place in that area As the Idaho portion of the park is uninhabited, a jury of residents of both the state and district could not be empaneled. As the Constitution guarantees the right to a jury trial, specified three separate times (Article III, Section 2; 6th Amendment; 7th Amendment), a defendant facing any felony or misdemeanor charge, being unable to receive a constitutional trial, could not be legally punished regardless of guilt or innocence.
The constitutional loophole in this area was discovered by Michigan State University law professor Brian C. Kalt while he was planning to write an essay about technicalities of the Sixth Amendment, which entitles criminal defendants to a fair and quick trial. The essay, which is called "The Perfect Crime", was published in 2005 in The Georgetown Law Journal. After Kalt discovered the loophole, he worked to have Congress close it. However, Congress ignored Kalt's suggestion.
So, IRL, there is such a place, but it is in Idaho not Montana and would only apply to crimes committed in the Idaho section of the Park, If you kill someone on the ranch and dump the body in the Idaho section of the Park, you are still getting prosecuted in Montana state court.
A hell of a trial lawyer such as yourself, albeit with unconventional methods, should have known this.