Under Hague the end of a war and any formal "Occupation" would be a peace treaty. Once all sides had withdrawn to their respective agree/negotiated positions, and civilian government returned to formerly militarily-Occupied areas...the rule of civil law would of course apply once again. For instance - the modern War Crime Court sitting at the Hague is a civilian court...
In Germany at the end of WWI this did not happen - for he Allies "abolished" the state of Germany for some years, and the Occupation governments were of course MILITARY ones - the Amerians weren't behind the fence at admiting to this, in the name "OMGUS"
"Occupation Military Government, U.S." So of course, there being no automatic return to civil government or civil law at the end of WWII in Europe - the War Crimes trials at the IMT had to be held under Martial law.It should be noted that because of the way the Allies abolished the state of Germany and imposed military government - the situation in Germany after the end of the ar was NOT as covered/expected/envisioned by Hague
So the War Crimes trials there under military law should be seen as exceptional, rather than the norm