D-1 The Oath
The information here is take from Fandom/wiki the link is belowIn order to become a citizen in the Federation, a civilian must serve in the Federation or another capacity such as teaching, being experimental subjects, for at least two years.
In order to ensure that only those who are serious about joining the Federal Service are accepted, the government places a double or even triple amputee at the front desk. This sends a message that time in the Federal Service is indeed dangerous.
http://starshiptroopers.wikia.com/wiki/Federal_Service
-The Oath-
I, being of legal age, of my own free will, without coercion, promise, or inducement of any sort, after having been duly advised and warned of the meaning and consequences of this oath, do now enroll in the Military Service of the United Citizen Federation for a term of not less than two years and as much longer as may be required by the needs of the service. I swear to uphold and defend the Constitution of the Federation against all its enemies on or off world, to protect and defend the Constitutional liberties and privileges of all its citizens and lawful residents of the Federation, its associated states and territories. such duties of any lawful nature as may be assigned to me by direct or appointed authority, and to obey all lawful orders of the Head of Operation and of all officers or appointed persons placed over me.