03USMC
Active member
Unfortunately it has been so long since the military has executed anyone that what method would be used is not clear.
http://www.nytimes.com/2008/07/29/u...ner=permalink&exprod=permalink&pagewanted=all
I would say that if convicted in US Military court, he may never be executed.
Last Military execution was 1961.
Method of execution is the purview of the convicting Judge of the Court Martial.
However may be over ridden by the convening authority the Chief of Staff, Sec Army or POTUS.
Leavenworth has a lethal injection chamber it most likely would be used to stem bad PR of a firing squad or hanging.