I was playing a NCR trooper character and I noticed that there's a trick with wearing the armor that keeps Legion Assassins from spawning as you move around the Mojave. All though your faction does change if you're seen killing Legion while wearing it if you remove and put the armor back on your faction with the Legion resets to neutral. Regular Legion will still attack you if they see you because you're in NCR armor but the Legion Assassins won't appear if you go near their spawn points.

I tested this several times at the spawn point north of Old Lady Gibson's Scrap Yard by Novac. Wearing the armor the assassins didn't spawn but wearing regular clothes they did.

Could anyone with a Legion character test this trick with NCR hit squads?