I believe he Navy Cross is a precursor to the MOH.
I checked out the Medal of Honor website and there's no straight answer:
http://www.cmohs.org/medal.htm
In the USSC I cannot find a section where on medal can prohibit another:
Sec. 3741. Medal of honor: award
The President may award, and present in the name of Congress, a
medal of honor of appropriate design, with ribbons and
appurtenances, to a person who while a member of the Army,
distinguished himself conspicuously by gallantry and intrepidity at
the risk of his life above and beyond the call of duty -
(1) while engaged in an action against an enemy of the United
States;
(2) while engaged in military operations involving conflict
with an opposing foreign force; or
(3) while serving with friendly foreign forces engaged in an
armed conflict against an opposing armed force in which the
United States is not a belligerent party.
'I believe he Navy Cross is a precursor to the MOH.'
Not a precursor, but a valor medal for actions deemed not to MOH standards. I'll admit I haven't done any research on it, but as a Marine, I have never seen dual valor awards for the same action. By the way, this is no slap at the 1stSgt, a Navy Cross is not small taters. Apparently in the opinion of his superiors, the conduct didn't meet the highest standard required. As a Navy Cross holder he joins the ranks of some amazing folks who did amazing things under fire.
http://www.history.navy.mil/medals/navcross.htm From the site: "The United States, with the Medal of Honor as its sole decoration, was caught unprepared not only for this custom, but also had no appropriate award to recognize heroism of a level less than that which would merit the Medal of Honor and no decoration to reward the myriad acts of meritorious non-combat service that the war would spur."
"As enacted 04 Feb. 1919, the Navy Cross was the naval services third-highest award and could be awarded for both combat heroism and for other distinguished service. Many, for instance, were earned for extraordinary diving and salvage feats. As originally third in precedence behind the Medal or Honor and the Navy Distinguished Service Medal, more than one Navy Cross recipient regarded its award as a "snub" in lieu of the Distinguished Service Medal.
The same act established the Distinguished Service Medal. Both decorations could be awarded retroactive to 06 April 1917. It would be 23 years and a 07 Aug. 1942 action by Congress that would place the Navy Cross just beneath the Medal of Honor, and limit its award to combat-only recognition."
"Presently, the Navy Cross is awarded to a person who distinguishes himself or herself by extraordinary heroism not justifying the award of the Medal of Honor. To warrant this distinctive decoration, the act or the execution of duty must be performed in the presence of great danger or at great personal risk.
The 1942 legislation synchronized the Army and Navy's "Pyramid of Honor," eliminated the dual combat/noncombat award of the Medal of Honor and Navy Cross and brought several previously Army-only decorations into the naval service."