It's a puzzlement to me why "regime" and "regimen" are confused.
"Regime" is what just happened in Libya…a revolution overthrowing the Qaddafi regime…an authoritarian government. Regime change.
"Regimen" is a disciplined procedure — a routine — like a training schedule to prepare for an athletic event; the careful preparations made for medical surgery; or the procedure that precedes a duel.
There was certainly some semblance of a regimen making it possible to overthrow the Qaddafi regime.