The Executive branch will not point a gun at itself and threaten to throw itself in jail if it does not comply ...
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That’s why the legislative branch must threaten to impeach (like they did to Trump). If they do not, then Supreme Court decisions really don’t matter if the Executive branch doesn’t enforce them.
So in the current political landscape, there is no Constitutional mechanism available to force the Executive branch to fulfill its Constitutionally mandated duty of protecting the border.