A video from Democrats calling on the military to refuse to obey illegal orders pushed the president into a frenzy.
www.ms.now
For making sure that our military knows that they do not have to obey illegal orders from their leaders, the Sec of Defense or the president. Be respectful about it, say "No Sir or No Mam, that order is illegal, and therefore I am not Constitutionally bound to obey it." You are protected by the Uniform Code of Military Justice, or UCMJ.
Now we all know that the president and his Sec of Defense, not being the brightest crackers in the barrel, will threaten you with all sorts of dire consequences if you refuse to obey an illegal order. But, stand firm, the courts will back you up. It might pay to remind them of the Nuremberg trials after WWII.