Federation of Humanity Series by Christopher Anvil

The crew of the ship were marooned on a planet with no ship repair facilities, where the well-meaning schemes of social engineers had created a nightmare of battling gangs. They had their own invention with them-an emotional amplifier, which could cause anyone to feel a heightened emotion, but this wasn't useful at first. If they heightened the locals' sense of pride, they took pride in becoming better criminals... moreThe crew of the ship were marooned on a planet with no ship repair facilities, where the well-meaning schemes of social engineers had created a nightmare of battling gangs. They had their own invention with them-an emotional amplifier, which could cause anyone to feel a heightened emotion, but this wasn't useful at first. If they heightened the locals' sense of pride, they took pride in becoming better criminals. So they pretended to be the Royal Legions, sent by a distant star kingdom in pursuit of an all-powerful villain who was hiding on the planet. Things were going better than they could have hoped, and the planet was rapidly becoming civilized . . . and then the real Royal flagship showed up. They thought they were doomed-but instead they were told they had shown just the type of initiative and intelligence that the new arrivals were looking for. So they were inducted into the Interstellar Patrol. And that was just the beginning. . . . less

Vaughan Roberts and his two companions had been trapped on a crime-ridden, chaotic planet until they bamboozled the population with a gigantic hoax - which brought them to the attention of the Interstellar Patrol, who were looking for a few good con men. In their first assignments, the new recruits performed admirably, so they naturally were given more tough nuts to crack, including: Flummoxing an alien empire which has taken a number of human prisoners as reconnaissance for an invasion.. moreVaughan Roberts and his two companions had been trapped on a crime-ridden, chaotic planet until they bamboozled the population with a gigantic hoax - which brought them to the attention of the Interstellar Patrol, who were looking for a few good con men. In their first assignments, the new recruits performed admirably, so they naturally were given more tough nuts to crack, including: Flummoxing an alien empire which has taken a number of human prisoners as reconnaissance for an invasion...stopping a scheme by not-so-good Samaritans pretending to lure a plague - which they introduced to the planet - with a miracle drug which is also highly addictive and can be supplied only by the schemers...making sure that the rightful heir to a planet's throne escapes from captivity and overthrows the usurper. This time there's a complication: Roberts may be falling for the ruler's beautiful sister...And much more. less