This may be something else.
Maybe lowering the BOOM on California sanctuary state? Hard to say, really. If that's it, I will buy the Marines some beers when they get here.
Border patrol support.
The arrest of the California Legislature, the Governor of California, and the mayors of certain cities. It would put the local and state police on notice not to interfere with a federal action.
(Yes, I'm grasping at straws here.)
But there is a precedent left over from the Civil War. Ten southern states were combined into five military districts and stripped of their statehood. They had to jump through certain hoops to be readmitted.
In 1939, the Supreme Court in Coleman v. Miller elected not to open that can of worms because the Civil War was not that far in the past. So the precedent stands.