Colsec Series by Douglas Arthur Hill

When a space craft carrying twelve youthful offenders, who have in someway rebelled against the Earth's harshly authoritarian society, crash lands on an alien planet, the six survivors must contend with the planet's hostile life forms.

Soon after being exiled to the planet Klydor, five young people begin to suspect that their struggle for survival is somehow linked to the rebel uprising against the Earth's harshly authoritarian government.

In this thrilling conclusion to the ColSec Trilogy, five young outcasts return from exile to free Earth from an authoritarian government. In the savage streets, they rally the Earth's people to fight for freedom.