Murder in the Gunroom (1953, not science fiction but rather a murder mystery) ISBN 1-882968-02-6
Crisis In 2140 (1957, with John J. McGuire, half of Ace Double D-227).
This was first serialized in Astounding Science Fiction as Null-ABC, copyright 1953.

Lone Star Planet (1958, originally A Planet for Texans) with John J. McGuire ISBN 0-441-24892-6.
The work is a clear and obvious tribute to H.L. Mencken's essay "The Malevolent Jobholder" (from The American Mercury, June 1924), in which Mencken proposed 
...that it shall be no longer malum in se for a citizen to pummel, cowhide, kick, gouge, cut, wound, bruise, maim, burn, club, bastinado, flay, or even lynch a [government] jobholder, and that it shall be malum prohibitum only to the extent that the punishment exceeds the jobholder's deserts.
The amount of this excess, if any, may be determined very conveniently by a petit jury, as other questions of guilt are now determined.

 In 1999, the novel won the Prometheus Award, Hall of Fame Award for Best Classic Libertarian SF Novel.
This tongue-in-cheek tale features a planet of Texans whose dinosaur-sized cattle have to be herded with tanks, and whose system of government derives its character from Mencken's essay.
The protagonist is an insubordinate junior diplomat who is appointed as ambassador to this cantankerously independent planet in the hope that he will be assassinated (as the previous ambassador had been), thereby justifying the forcible invasion and conquest of the Texans.
The crux of the story is the trial of the previous ambassador's assassins—actually paid killers hired by an alien empire also planning invasion—under a legal system that considers the killing of a practicing politician to be justifiable homicide.

First Cycle (1982, Michael Kurland expanded this from a Piper outline) ISBN 0-441-23919-6
Murder in the Gunroom (1953, not science fiction but rather a murder mystery) ISBN 1-882968-02-6
Crisis In 2140 (1957, with John J. McGuire, half of Ace Double D-227). This was first serialized in Astounding Science Fiction as Null-ABC, copyright 1953.
Lone Star Planet (1958, originally A Planet for Texans) with John J. McGuire ISBN 0-441-24892-6. The work is a clear and obvious tribute to H.L. Mencken's essay "The Malevolent Jobholder" (from The American Mercury, June 1924), in which Mencken proposed 
...that it shall be no longer malum in se for a citizen to pummel, cowhide, kick, gouge, cut, wound, bruise, maim, burn, club, bastinado, flay, or even lynch a [government] jobholder, and that it shall be malum prohibitum only to the extent that the punishment exceeds the jobholder's deserts. The amount of this excess, if any, may be determined very conveniently by a petit jury, as other questions of guilt are now determined.
 In 1999, the novel won the Prometheus Award, Hall of Fame Award for Best Classic Libertarian SF Novel. This tongue-in-cheek tale features a planet of Texans whose dinosaur-sized cattle have to be herded with tanks, and whose system of government derives its character from Mencken's essay. The protagonist is an insubordinate junior diplomat who is appointed as ambassador to this cantankerously independent planet in the hope that he will be assassinated (as the previous ambassador had been), thereby justifying the forcible invasion and conquest of the Texans. The crux of the story is the trial of the previous ambassador's assassins—actually paid killers hired by an alien empire also planning invasion—under a legal system that considers the killing of a practicing politician to be justifiable homicide.
First Cycle (1982, Michael Kurland expanded this from a Piper outline) ISBN 0-441-23919-6
H. Beam Piper