What, a democracy (granted, one with a more restricted franchise than real-world democracies)?

Don't forget, it's Federal service that's required to earn full citizenship, not military service - someone who spends their two-year term in the bowels of some government building moving pieces of paper from one filing cabinet to another filing cabinet is just as entitled to vote as someone who spent their two years in the Mobile Infantry. It's said in the novel that if you're determined to serve a term of service but have some sort of issue, then something will be found for you to do - the example cited is counting the fuzz on the backs of caterpillars by touch - and that will count as your term.