They can't. It was highly unlawful to refuse to pass down orders from the CiC, and that's exactly what they did. I didn't trust the Military in that regards since 1/20/17. There was plenty of scuttlebutt going around back then when it was implied by many at the Pentagon, that Trump's commands were not absolute. That they would intervene to be a check on Trump, who they were insisting at the time that stupid Trump would walk us straight into WWIII.
They broke the chain of command to "save the world from Trump!"
This is the level of insubordination we're dealing with here.
Whereas the people they sided with were plotting and perhaps actually produced illegitimate results to the election of 2020...
and
Whereas having a violent, invasive protest was essential to acceptance of those potentially illegitimate results with a minimum of dissent and with the Congress in a state of fatigue which might well render their judgement less than fully alert...
and Whereas such violent behaviour on the part of protesters might have been incited, furthered, or otherwise enhanced by the presence of agents provocateur within the protest crowd operating under a false flag, and the presence of National Guard performing security would interfere with the desired outcomes above...
Those apparently desiring those results and enabling them to achieve their desired outcomes, especially those in the direct Military Chain of Command, who acted to subvert the desire of the then President of the United States to maintain order, in fact have acted against the interests of a smooth transition of power if legitimate, the addressing of any objections to that transition as is mandated by the Rules of Congress, and acted against the best interests of these United States: to wit, as enemies of the Republic.
If it can be shown that they did so with malice and aforethought, and in collusion, this would represent a criminal conspiracy under the US code and the UCMJ as those bodies of law applied to the respective participants, and quite possibly, treason.
At the very least, the refusal to execute the orders of the Commander in Chief is a serious violation of the UCMJ, and should be tried by Military Tribunal, and in the event of a guilty verdict, punished appropriately.