My answer to Can the US forces commanders reject any unreasonable command of the US president?
Answer by Desmond Last:
All orders given, received and executed must be legal. There is no legal excuse or standing for illegal orders.
It is not an excuse, reason or justification to state when asked as to the reason an order was executed which was in contravention of the law to state ‘I was ordered to carry out the actions I took’.
This principle was set by the Nuremberg Courts at the end of World War Two.
Many high-ranking Officers of the Nazi Party and the German Army gave the reason they committed the killings and ill-treatment of civilians was because ‘they were ordered to do so’.
The Court rejected their defense and they were found guilty and sentenced to death or life imprisonment.
It is this Principle which will one day be used when the Law is used to bring to Justice those who have knowingly killed civilians in the Syrian Civil War.
There is no Law, Military or Civilian which allows the killing of Innocent Civilians.
There is no exemption in the International Convention of Human Rights for Military Action which intentionally kills civilians.
An order which breaks the Law should not be obeyed. Taking part in a situation which the Law judges as illegal is breaking the Law.
Allowing a situation which is illegal to exist when you have the legal ability to stop that situation from continuing is breaking the law.
There is only one Legal System and there is only one Jurisdiction for each of the relevant National and International Laws.
Should General Sir Nicholas Carter of the United Kingdom Armed or for that matter General Joseph Dunford of the USMC allow their command to take part in a situation which is in contravention of both National and International Law they would be guilty of breaking those Laws. As would the men in their command.
The answer to the Question is that any illegal order by a President should not be carried out by any soldier.
An order that is legal must be carried out. It would be up to the Military command to explain to the President that logistics, manpower, unnecessary loss of life or certain defeat may make it not possible to carry out a particular order.