Hello Geenie,
Firstly, here a good read
http://www.dod.mil/dodgc/doha/5200.2-R.pdf
Specifically Appendix 8c(3) pp139
"Conditions that could raise a security concern and may be disqualifying include:
(1) the exercise of dual citizenship;
(2) possession and/or use of a foreign passport;
(3) military service or a willingness to bear arms for a foreign country;
(4) accepting educational, medical, or other benefits, such as retirement and social welfare, from a foreign country;
(5) residence in a foreign country to meet citizenship requirements;
(6) using foreign citizenship to protect financial or business interests in another country;
(7) seeking or holding political office in the foreign country;
(8) voting in foreign elections; and
(9) performing or attempting to perform duties, or otherwise acting, so as to serve the interests of another government in preference to the interests of the United States.
DoD 5200.2-R, January 1987
Conditions that could mitigate security concerns include:
(1) dual citizenship is based solely on parents' citizenship or birth in a foreign country;
(2) indicators of possible foreign preference (e.g., foreign military service) occurred before obtaining United States citizenship;
(3) activity is sanctioned by the United States;
(4) individual has expressed a willingness to renounce dual citizenship.
Interestingly, apparently "willingness" changed in the last few years, as most contries actually simply don't have regulations that even allow someone to revoke their citizenship, the US does, but is one of the few. Apparently all that is required now is a letter stating that you are willing to revoke your citizenship. When I contacted my "other" country government employee in charge of such things, she laughed and said, "sure send me the letter of revokation, I'll put it in my top draw with all the others"
Secondly,
One resource to take note of is the "DOD Security Clearance review board" that publish most of its findings ever year.
Link =
http://www.dod.mil/dodgc/doha/industrial/2010.html
My limited understanding is that if a clearance request is at all dubious, it is rejected and then an appeal can be heard by this board, so in essence this board decides where the line in the sand is drawn.
If the regs are ambigious on an issue then it is likely that this board will have created some precedence on the mater.
I recommend you cut and paste this into a word document and use the search function.
Note: This document only covers civilian contractor’s hearings, I would hazard a guess that the precedence created would follow over to the uniformed side of the house, but that is a total uneducated guess.
I'm not sure where, if at all, the uniformed hearings are published.
Others here, will be able to clear up these questions
Hope this helps
Scimitar