This subsection of the military works to keep the Strip safe alongside the securitrons, mostly to stop NCR citizens and soldiers on leave from making a fool of themselves and the NCR. Because of a treaty made with Mr. House, they are not allowed to have guns on The Strip, so they use non-lethal cattle prods as a substitute.
xbox360pc NCR trooper MPs may randomly approach the Courier after you have spoken with NPCs such as travelers on the Strip, the only response that can be got from them is "I need to get going". [verified]
xbox360pc Rarely, they might approach you, and tell you that "they finally got you and you are going to pay", and then they will turn hostile. Anyone near the MP Trooper will also turn hostile against you, including Securitrons. If this happens on the NCR Embassy, your infamy with the NCR will become extremely negative, regardless of how much positive fame you have with the NCR (e.g. Idolized becomes Wild Child). [verified]