It's illegal for one branch of the government to cooperate with another to enforce the border. Meanwhile, abandoning the border (despite a legal obligation to enforce it), and even sabotaging states from stepping in to fix federal neglect and establish the border they are owed, is perfectly legal [1].
"The rule of law"
[1] https://www.npr.org/2024/01/22/1226142790/supreme-court-texa...