“According to the sources, the President has asked the Joint Special Operations Command (JSOC) to prepare the invasion plan, but it is being resisted by the joint chiefs of staff on the grounds that it would be illegal - and would not be supported by Congress.”
“A diplomatic source said: 'The generals think Trump's Greenland plan is crazy and illegal. So they are trying to deflect him with other major military operations. They say it's like dealing with a five-year-old'”
I mean this came up several times in court. It's totally legal for him to order these things. It might be illegal for the generals to act on those orders. But then, because the order is legal by virtue of the officeholder issuing it then it's also illegal to refuse a lawful order. Only one set of illegal orders comes with a pardon though.
It's still one's duty to refuse an immoral order. The Allies convicted Nazis on that basis at Nuremberg, and "just following orders" was famously invalidated there.
“A diplomatic source said: 'The generals think Trump's Greenland plan is crazy and illegal. So they are trying to deflect him with other major military operations. They say it's like dealing with a five-year-old'”