Source; J Coles
Guys & guyettes ... ain't no such thing as 'national martial law.' There is no mechanism for a national leader to declare 'martial law' in all the land. Because no one has challenged them, in court or tried to nullify them via legislation. The Executive Branch, through a number of ExOrds & Presidential Findings, has claimed the right/power to declare a 'state of emergency' on Federally owned land (of which there is way more than the Constitution allows -- more on that later) ...
The Posse Comitatus, even in its current weakened form, prohibits use of Federal forces to enforce any unconstitutional law or edict. Further, the 10th Amendment prohibits the Federal Government from subsuming the rights,powers and, or responsibilities of the states.
One of my jobs in political-military affairs was to forge 'civil support agreements' between DoD & state/county/municipal governments. Under current law, the Feds can't do anything until the highest civil authority in an area -- usually the state Governor -- initiates the process of enlisting Federal involvement in the state's problem: in essence, the Governor must declare that the issue is beyond the ability of state resource to handle the issue -- and the Governor must state clearly which Federal resources are needed -- but the list of available resources is not open-ended: having Federal officers, agents or other Federal law enforcers/active component or even Federalized state forces perform civil law enforcement is not on the list.
The most the Feds can do during use of civil support agreements is provide a wide variety of equipment, both Federal non-military and military & "standby contract" civilian agents is support to local law enforcement & emergency management organizations.
Since Katrina, no fewer than six Federal trial courts & appeals courts have ruled that law enforcement MAY NOT CONFISCATE CIVILIAN WEAPONS.
Now, for the matter of 'Federal Lands.' The Constitution lays out pretty clearly that Federal lands should be no bigger than the footprint of 'necessary Federal buildings' and 'as required for military training grounds & facilities.' Legislation can never supersede or take precedence over the Constitution. Ergo, the laws passed in the 19th-Century that created the national parks system & the 20th-Century that created national monuments & conservation areas are UNCONSTITUTIONAL on their face.
Thus a Federal state of emergency should impact a very small portion of the population, largely because even if these huge swaths of land are allowed to continue they are sparsely populated.
As I see it, only deep blue, commie-zombie Governors will invite the Feds in during a national emergency. Governors like mine will tell the Feds to pound sand.