Go to Mars. Build a colony that does not need anything from Earth, declare sovereignty. I can see no reason if some group of people were able to do this they could not declare their rights to be free from a planet they do not live on. At that point it would be up to Earth (anyway who is Earth here, who do I call to speak to the president of earth?) to enforce compliance with their sovereignty and at the point that Mars could stand alone, I would think that they would have mastered the art of astroid capture and movement which could make things bloody pretty quickly.