Hm... the Citizenry is extremely powerful, their bio-weapons are capable of killing GLs, and their personal gear is on a level to both defend and take hits on a level to be a threat here.
Kryptonians, though, are kryptonians... but of course, only a fraction of them are at all good fighters, and the Citizenry fight with massive experience.
They'll need to pull out more ships than they did in the invasion of Earth, but they'll win.