Space Cossacks

"A long way to spinward it seemed. It would be a years journey just to get there. I could see why it had caught his imagination. It was much like the journey our ancestors had made from distant Terra... "You could come too", he finally said, "Bring Ilja and the children. Build a home out there where it will mean something. "It means something here", I said. "Does it? Look up there", he growled, "We're fenced in. Arrogant Imperials, spooky Zhodani... Nothing remains for us to grow unless we break out of the cage entirely... I slapped his shoulder in good cheer. "No doubt you're right. Still most of us will never be able to go with you. Someone has to stay behind to defend our homes, even if the fight is doomed"

- GURPS Traveller: Sword Worlds, P.127

"Imperial authority tolerated the Kimashargu for a time but eventually cracked down on the movement about AD 950 Many thousands of Kimishargu fled Imperial space entirely, settling beyond the rimward frontier"

- GURPS Traveller: Interstellar Wars P. 19

There is no hope and You Can't Go Home Again. The Empire is spreading out. Even The Federation has too many Obstructive Bureaucrats. There is no way for free men to get out of the reaches of The Government and even mounting La Résistance will be of no avail. So what do you do? You become Space Cossacks. You flee to the border and live in a tough area where you all have to be sharp. You set up as Space Pirates or as Hired Guns or as Intrepid Merchants. Or all of these at once. With you are various dissidents like people who feared being Made a Slave. There might be a Noble Fugitive or two, perhaps even a Defector From Decadence. You and your brave band of Fire-Forged Friends will struggle on to survive and maintain your freedom and heed no laws but your own and respect no authority but that of your Team Mom and/or Team Dad. Songs will be written of your deeds.

The Empire most likely officially considers these guys outlaws, either in the sense that they're to be shot on sight, or in the sense that they're "outside the law" and are to be left alone as long as they stay out of the way. Either way, they probably consider them useful, as they both screen the empire from external threats and tame the fringe worlds into a state ready to be colonised. They may also provide a handy place to send people who are to be Reassigned to Antarctica.

Given the parallels to the Wild West, a Space Western is almost sure to be set amongst such people.

The reference comes from the old Russian custom of disgruntled people fleeing to the steppes and joining a Cossack band.

Film

 * Star Wars: Han Solo
 * Han himself is more of a Defector From Decadence, being former Imperial officer and all, but the underworld he joined fits this to a T.
 * The entire human species became Space Cossacks in Titan A.E. after the destruction of the Earth.

Literature

 * At one part of Dune it is hinted that the Guild will transport exiles outside the Empire for the right price.
 * Ah, but it's not so much that the exiles become Space Cossacks, they're simply resettled on certain Guild-controlled worlds that are more or less off the official charts.
 * It's kind of the same thing; the original cossacks didn't lose contact with the Czar and often fought for him. They simply went to places where they could keep him at arms length.
 * Fremen might count; according to their legends they were originally runaway slaves.
 * The Hyperion Cantos has the Ousters, who fit this trope quite nicely.
 * This was the background for H. Beam Piper's Space Vikings, in the book of the same title. "at the end of the Big War. Ten thousand men and women on Abigor, refusing to surrender, had taken the remnant of the System States Alliance navy to space, seeking a world the Federation had never heard of and wouldn't find for a long time." Eight centuries later, their descendants have begun raiding into the territory once held by the now-collapsed Terran Federation.
 * The Nomads in The Peregrine lead a gypsy like existence with each ship being a clan of it's own and tribal law being based on their ships(incest for instance is simply copulating with someone born on your own ship rather then transferred via marriage). They meet periodically to discuss gossip, bid for temporary exclusive claims to a trade route or whatever, talk of matters of general interest and try court cases.

Live-Action TV

 * Firefly: "...take me out to the Black, tell them I ain't coming back"
 * In Star Trek: Deep Space Nine the settlers on the Cardassian frontier are rebelling against both the Federation and the Cardassians. They are usually treated semi-sympathetically even though they are sometimes adversaries.

Tabletop Games

 * In the BattleTech universe, there are the Clans. They are an interesting example as by the beginning of the main storyline they have become the dominant power in their own space and hold many systems of their own. Their warrior culture is enforced rather than necessary.
 * Traveller: Has a lot of examples of this. Among them are the Vilani Kimashargur, The Classic Traveller volume "Pocket Empires". And much of the history of the Sword Worlds as well as this troppers favorite sample campaign from the Gurps volume of that name. Many others.

Video Games

 * Raynor's forces in StarCraft are an example if this.