Wikipedia agrees with you. https://en.wikipedia.org/wiki/Terran_Federation_(Starship_Troopers)

'The people of the Terran Federation are either "Citizens" or "Civilians". Everyone is born a "Civilian", and at age 18 every "Civilian" has the right to enroll for a minimal 2-year term of "Federal Service". In theory a completed term of Federal Service ensures a "Citizen" is willing to put the needs of the community before their own personal well-being. This is because Federal Service is tough and dangerous (by design). It can involve joining the military, being a human guinea pig, testing survival equipment, or manual labour. The Federation makes it quite easy to quit a term of service before completion (even during war-time), but once someone has quit they are never allowed to enroll again. This is to ensure that all volunteers are dedicated, whilst also discouraging people from leaving.

The Federation makes the opportunity of Federal Service open to everyone, able-bodied or not. A doctor giving a medical examination says "if you came in here in a wheelchair and blind in both eyes and were silly enough to insist on enrolling, they would find you something silly to match. Counting the fuzz on a caterpillar by touch, maybe." The only impediment that can render one ineligible for federal service is if a psychiatrist determines that one cannot understand the oath of service.'

Fixed.