I knew an NCO who was a former Surface Warfare Officer in the Soviet Navy hunting American submarines in the North Atlantic who immigrated to the United States and eventually became a SIGINT 35P and worked as the NCOIC for the Army Division G2 SIGINT shop regionally aligned with Europe. We have a 350F who was a SIGINTer here at the school house that NSA did not approve access to their systems (was a 352N) and forced to switch to 350F. I've got a buddy of mine who is the Russia Analyst for a CCMD J2 who's wife is from Russia. Someone I marched over 100 miles with was from Russia, enlisted into the reserve component as a 35M and is now an intel officer.
It's fairly common. We have a rich history of immigrants working in intelligence, and sometimes it doesn't work out, but usually it does. Some of those most dedicated to America are the ones who escaped some serious hell holes.
I’m not saying that foreigners can’t be trusted, I have worked with people that have come over from Eastern Europe and former soviet countries, growing up in less than ideal conditions, and they are probably some of the best Americans around because they have different experiences and perspectives. I just thought that it would have been a conflict of interest to have a father in law that was actively serving as a Russian military officer.