No, that's not a law firm, although it would have made an interesting one. They are united by this two-parter of Cheyenne, the 1941 movie "They Died With Their Boots On" and the 1876 battle both were based on, the Little Bighorn.
They Died With Their Boots On was the #1 movie of my youth. A local channel had a package of movies from Warner Brothers and this, at least to the kids on my street, was the gem of the collection. We'd watch it on our porch while my Mom served Lemonade and when it was over, go out into the back yard, refight the battle, arguing about who would get to be Custer this time.
Custer has been a lightning rod for criticism though our history. When we need a villain, he will absorb all of our blame. When we need a hero, he can be reinflated to one. In 1941 we needed heroes so the cinema's greatest hero at the time, Errol Flynn, played him. He was depicted as a flamboyant, self-involved and ambitious soldier but also a man of integrity who gets drawn into a conflict with Native Americans, whom he respects. The villains are the speculators and politicians who created the Gold Rush into the Black Hills.
Here he is played by the far less charismatic Lee Atwater as a realist looking for a military victory. Members of his command have contempt for the Native Americans, but he never voices any prejudicial view. Those conniving politicians are still the bad guys.
On You-Tube is an interview with Marlon Brando on the Dick Cavett Show in which he said that "Hollywood's view of Native Americans is that the only good Indian is a dead Indian. I grew up watching movie and TV westerns and I've never heard a hero or anyone else we are supposed to admire express such a view. Here Cheyenne actually dons the clothes of the tribe who raised him and views the battle in full Indian regalia, (but as a prisoner of the Sioux, who do not trust him). He went there to try to prevent the conflict.
The episode uses clips from TDWTBO and is thus a prisoner of the errors there, which shows the battle taking place in an arid plain and Custer lured into the battle by a small group of mounted warriors. It's a great battle scene but there's no river and no Indian village in sight. Also no Reno or Benteen.
Some reviewers have complained about Lorne Greene's performance as the prosecuting office in the trial of Reno. He's essentially playing the same character he played in 1957's Peyton Place, (the movie), and in the same swarmy way. He's a prosecutor with an ulterior motive. In Peyton Place, he's looking to run for Governor. Here he's in with the corrupt politicians who started the whole mess and making a scapegoat of Reno and a martyr of Custer to further their ambitions to take over the Black Hills. In both cases the part was written, and he would have bene directed to play it that way. Interestingly, this episode aired January 11, 1960. Bonanza premiered 9/12/59. Cheyenne was part of a wheel with Sugarfoot and Bronco so it's episodes could have been filmed far in advance of the broadcast dates. This may have been the very last thing Greene did before he became Ben Cartwright.