There is no provision for anything other than orders and following them.
There might be a congressperson or robed wonder wandering around, but that they would be listened to is beyond dubious into laughable. They'll be told to sit down and shutup. Pick a disaster or emergency that is historically available for review and anyone can see it for themselves.
The federal governments plan for a BIG emergency is exactly the same as for a MEDIUM emergency like we have been under for years now, and that is rule by the executive branch, refined under fema, renamed the patriot act, ongoing for years under an "emergency powers decree", that "allows" such niceties as one single human being ordering the nation to war, and everything under that..
They OWN you 100% right now, so to think they will own you less is silly. Anything you own is subject to confiscation. Your very person is subject to confiscation. These are the "laws" and can be looked up and referenced, I'd bet a dime to a dollar raising freeperthon donut they have been posted here dozens of times already, mostly to be forgotten, or een worse, trivilaised or denied that they exist..
The congressional and judicial branches currently are no more than a public facade for the legitimacy of the stealth coup that has taken over the united states. It's window dressing to keep people all serious about 'elections" and whatnot, like they are willing to actually let you "rule" yourselves should you choose to again now that you don't. They are just spelling it out in little words now so that people can start coming to grips with the reality of it. They have to do it in stages, and in different manners to inform the different levels of the public and their various awarness levels out there, this is just another stage.. They have little need nor less inclination to keep wasting their time for much longer on maintaining the illusion that we have a representative republic.
You should write for SNL.