If the courts rule Trump's command illegal and Trump ignores the court ruling and commands the troops to do again what the court ruled unconstitutional/unlawful, what should the soldiers do?
It depends on what the goal of each individual soldier would be in that situation.
Can you give me an example of a soldier in that situation and what that soldiers goal would be?
For example, if the goal is to stay out of trouble and continue their service to their country, the clear choice is to obey orders and read in the news later about any final resolution of legal cases in the USSC.
If the goal were to make his commander in chief look bad, somehow, and that soldier were willing to sacrifice his or her career, freedom, standing in the community, and all federal benefits, in order to make some kind of political statement, I suppose those congressfolk's advice might be taken.
If he or she were one of their consituents, then they - especially Mark Kelly, who knows better than to act like he's acting - would serve him or her best by advising him to take the first option.
But, I could be wrong. Are there precedent cases of soldiers rightfully disobeying orders because political opponents of the CiC are trying to stall military actions through the courts?