Allegations that Mattis is intervening regularly to avert national security disasters have once again raised the question of whether military commanders possess the authority to refuse a direct order from the President under certain circumstances.

The reality is that the only basis for interfering with a direct order is if it’s illegal, immoral or unethical. And there is a widely held belief among military commanders that they must resign if they are unable to carry out an order that does not rise to that standard.

Speaking publicly on the issue last November, Gen. John Hyten, top US nuclear commander, said he would push back against an order from Trump for a nuclear strike if it were “illegal.”

Can military commanders refuse an order from Trump? – CNNPolitics

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