And no, there are no spoilers what so ever.
The Individual vs. the State.-->
The relationship between the individual and state in Starship Troopers is very similar in having the attitude of: ask not what your country may do for you, but what you may do for your country. It is taken for granted that a person must contribute something to the nation, by way of service, before they are allowed to vote and be part of the government. It is also accepted that everyone, except in certain cases, has the right to serve the nation and therefore earn the privilege of voting and being part of the government.
People are not restricted from serving because of poor health; as a doctor said to John, “if you came in here in a wheel chair and blind in both eyes and were silly enough to insist on enrolling, they would find something silly enough to match” (32.) Whatever a person’s limitations, they have a right to serve. The only reason a person might be excluded from being allowed to serve their time is if they were deemed unable to understand the oath they must take and what it means; the explanation is not stated, but it is probably not only because it is not fair to hold someone to an oath they do not understand, but also because anyone incapable of understanding the oath would not be found desirable to serve the government.