Mists of Mars - George A. Whittington

The Wild West, reimagined as the Martian landscape, where law is defined by whoever has the biggest weapons, be they guns, ships, or things more mysterious. As stand-ins for Indigenous Americans, the Martians themselves.

When Barry Williams, special investigator for the Terrestrial Bureau of Martian Affairs, finds out the state of play, he seeks to change the status quo and relieve destruction and suffering. He's going up against the nature of law itself. - Summary by Edmund Bloxam