is the Uniform Code of Military Justice
for the United States
. All members of the US Military are subject to the Code. The UCMJ can be considered an additional set of rules and laws
outside of the civilian world
If a military member or person subject to the rules and provisions of the UCMJ get charged with Driving While Intoxicated (DWI) by the local police department, and they are charged and convicted in a civil court, they can then be charged for the exact same offense under the UCMJ and get an additional sentence or fine. This was a simplified example, and there are more factors involved in double-jeapordy cases, but you get the general idea.
Conviction for violating an article of the UCMJ can mean anything from a permanent letter in your file to a dishonorable discharge to incarceration to even death. Note that if you are charged with a crime in the civilian side and are found not guilty, you can get charged again and have to go through the entire process again under the UCMJ rules.
The complete UCMJ can be viewed in its legal jargon-infested glory at http://jaglink.jag.af.mil
I considered noding the entire UCMJ (it is not copyrighted), but I figure that I would spare you from finding it in the random links box, a la the Windows Error Message writeups from hell.
(From the Chatterbox) Byzantine says, "May I suggest adding a note to UCMJ such that Reserve and National Guard members of the military are only subject to said code while on active duty?"
Couldn't have said it any better, thank you Byzantine.