Someone in prison for reasons outside of the normal criminal-justice process. Possibly because the person's politics is deemed inimical to the stability (real or imagined) of the state (see: Nelson Mandela). Or maybe because the person's uppitiness (as an activist member of a minority) has caused him/her to be framed for a crime and/or not given a fair shake in the justice system (see: Leonard Peltier, Mumia Abu-Jamal). It might be
"Because I said so."
(see:
War on Some Drugs).