There's no need for violence or space rockets. Rather apply a more boring approach: cut supplies and wait patiently, which basically amounts to doing nothing. I

There's no need for violence or space rockets. Rather apply a more boring approach: cut supplies and wait patiently, which basically amounts to doing nothing. If the space ship/colony is self sufficient and can operate without supllies, then it can probably declare independence. Anyone not content with that can apply diplomatic pressure or start a space war over it.