Why, exactly, don't we use the military to stop the invasion? The Constitution explicitly mandates that the federal government protect the States from invasion (A4S4) and authorizes the Congress to pass laws concerning military response to invasion (A1S8CL15).
> A4S4
> The United States shall guarantee to every State in this Union a Republican Form of Government, and SHALL PROTECT EACH OF THEM AGAINST INVASION; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened), against domestic Violence.
(emph. added)
>But posse comitatus!!
Oh, you mean this?
>18 U.S. Code §1385. Use of Army and Air Force as posse comitatus
>Whoever, EXCEPT IN CASES AND UNDER CIRCUMSTANCES EXPRESSLY AUTHORIZED BY THE CONSTITUTION or Act of Congress, willfully uses any part of the Army or the Air Force as a posse comitatus or otherwise to execute the laws shall be fined under this title or imprisoned not more than two years, or both.
(emp. added)
>But optics!!
Really? We're at the point where many people disbelieve deportations will ever happen; and you either have both the WILL and ABILITY to defend your borders, or you don't have a country.