#aradesh

theory 1: the Desert Rangers have been in somewhat steady contact/alliance with the NCR from its inception due to their generally aligned values and mission statement. it could also just as easily have been purely due to geopolitical reality. back then their borders wouldn't have touched, and the NCR wasn't even a big strong nationstate back then, so there's even less reason why the Desert Rangers could've been wary of the NCR.

this makes the Desert Rangers' extremely smooth future absorption into the NCR (not a single New Californian has a problem with them even only 10 years after their 'unification') even more believable.

theory 2: the New California Rangers had some version of the Desert Ranger armor even before the Unification due to its advanced armor capabilities and genuine usefulness. we know there were members of the DR in California way back in FO1, so it's not impossible they would've scavenged pre-War riot gear and made copies of it like the DR did