For decades now, there has been in force an Interstate Compact wherein at least 49 (last I checked, and it may now be 50) States agreed to assist each other in natural disasters and emergencies with their respective National Guards to reinforce and augment each other. This was definitely the case in 2005 during responses to Hurricane Katrina. The Interstate Compact was duly authorized/ratified by the Congress pursuant to Article I, section 10 of the Constitution.
One suspects this will also suffice to legalize the contribution by red States of their National Guards to assist the federal government, certainly in DC if not the other states as well.
The National Guard is a part of the state militia, but it's also more than that. For historical reasons recounted in Perpich v. Department of Defense, the National Guard also became part of the armed forces of the United States so the President could take the Guard where the militia couldn't go.
It's not just when in active duty. Members of the National Guard take two oaths: a State oath and a federal oath. Normally, they wear both hats.
Critical to your question, however, is that when ordered to active federal duty, a member is (usually) "relieved from duty in the National Guard of his State." 32 USC § 325(a).
So if members of the National Guard of Texas are ordered to active federal duty in Illinois, they don't go as members of the militia, but as members of the US armed forces.
FYI: Not my expertise either, but someone mentioned this to me years ago, so I knew to look for it.
Why do I believe that if California National Guard was ordered into Texas, both Texas and Trump would be apoplectic? Of course, Trump will not do so, but if Biden or Obama had, the Republicans en masse would stroke out.
Lincoln ended our first civil war. It seems Trump is hell-bent on fomenting our second ....
For decades now, there has been in force an Interstate Compact wherein at least 49 (last I checked, and it may now be 50) States agreed to assist each other in natural disasters and emergencies with their respective National Guards to reinforce and augment each other. This was definitely the case in 2005 during responses to Hurricane Katrina. The Interstate Compact was duly authorized/ratified by the Congress pursuant to Article I, section 10 of the Constitution.
One suspects this will also suffice to legalize the contribution by red States of their National Guards to assist the federal government, certainly in DC if not the other states as well.
Doesn’t that compact require the request/consent of the state where the guard goes?
It looks like an update to this piece might be timely - it no longer seems we can doubt the plans for interstate militia deployment
The National Guard is a part of the state militia, but it's also more than that. For historical reasons recounted in Perpich v. Department of Defense, the National Guard also became part of the armed forces of the United States so the President could take the Guard where the militia couldn't go.
It's not just when in active duty. Members of the National Guard take two oaths: a State oath and a federal oath. Normally, they wear both hats.
Critical to your question, however, is that when ordered to active federal duty, a member is (usually) "relieved from duty in the National Guard of his State." 32 USC § 325(a).
So if members of the National Guard of Texas are ordered to active federal duty in Illinois, they don't go as members of the militia, but as members of the US armed forces.
FYI: Not my expertise either, but someone mentioned this to me years ago, so I knew to look for it.
References
https://tile.loc.gov/storage-services/service/ll/usrep/usrep496/usrep496334/usrep496334.pdf (Perpich, discussing the history)
https://constitution.congress.gov/browse/essay/artI-S8-C16-1/ALDE_00013673/#ALDF_00027673 (more history)
https://www.law.cornell.edu/uscode/text/32/101 (definitions)
https://www.law.cornell.edu/uscode/text/10/246 (definition of militia)
https://www.law.cornell.edu/uscode/text/10/12406 (call into federal service)
https://www.law.cornell.edu/uscode/text/32/304 (enlistment oath)
On re-reading your post, it looks like you already knew this. Still, I enjoyed chasing down the history.
Why do I believe that if California National Guard was ordered into Texas, both Texas and Trump would be apoplectic? Of course, Trump will not do so, but if Biden or Obama had, the Republicans en masse would stroke out.
Lincoln ended our first civil war. It seems Trump is hell-bent on fomenting our second ....