"The Imperial Code of Military Justice". This I take to be a set of rules that sets forth how the Emperor wants his military forces to comport themselves. These rules are not a result of agreements with neighboring states, but they do in clude prohibitions against atrocities and whatnot
(In case you don't think any state would unilaterally impose limits on how they deal with their enemies, take a look at the Royal Navy's Articles of War (
http://www.io.com/gibbonsb/articles.html ) which includes several 'moral' articles. Check out Article 9, for example.)
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The Imperial Code of Military Justice may be like the Uniform Code of Military Justice used in teh US military. It mostly regulates criminal activities within the the armed forces. If you look at the link to the Yale website I put up it discusses the laws of war as found in international conventions and treaties and are agreements among different sovereign states. [e.g. not bayoneting wounded enemy combattants for fun and profit.]
The RN regulations are primarily for regulating their own service and are not binding on other navies.
Some believe and heve said that "laws of war" are really not possible because the losing side will discard them to win or that certain powers will adhere to them to keep the status quo.
In game terms the Imperial rules are loose and primarily intended to prevent the use of nuclear weapons and perhaps even massive and needless civililan casualties [or maybe not]
IMTU, overly sadistic savagery tends to beget the same in return and players who show no quarter can expect no quarter in return if they are captured.