I was playing Fallout NV and before I ever set my foot on NCRCF soil I had neutral reputation with Powder Gangers. I helped them out and when there was an option to kill NCR troopers on my way out, I went into "hidden" and put on NCR armor. I did not kill anyone but looted the bodies. NCR took the prison on their own.
After this I went into an auxilliary building and there were 2 Powder Gangers who somehow avoided the fate of their colleagues. I killed them without trying to be stealthy. Now when I enter the administrative building, NCR troopers are attacking me on sight. This is somewhat weird since I would think that I only helped them out clearing the place.
I got some positive NCR rep afterwards and now am "idolized" by them. Still, NCR troopers at NCRCF attack on sight.
There must be something weird about Fallout NV reputation system explaining this. What is it?
Best Answer
When you side with the Powder Gangers in I fought the law the NCR soldiers who attack the prison will always be hostile to you until they are killed, regardless of your reputation with the NCR.
If the NCR soldiers are killed by the Powder Gangers, via silenced guns, by melee/unarmed weapons, or while wearing NCR armor which you then take off you will not suffer reputation loss with the NCR and NCR soldiers outside of the prison should not be hostile to you.
If you kill the NCR soldiers without stealth or with an unsuppressed weapon you will suffer the normal reputation penalty and may make external NCR soldiers hostile to you.