Lets break this down
This part I am unsure of as the references don’t appear to match up. at least as far as my research.
NOW, THEREFORE, I, DONALD J. TRUMP, by the authority vested in me by the Constitution and the laws of the United States of America, including sections 201 and 301 of the National Emergencies Act (50 U.S.C. 1601 et seq.),
this part says he is calling up the ready reserve regardless of any other authority(iow:states can not pull their troops)
hereby declare that a national emergency exists at the southern border of the United States, and that section 12302 of title 10, United States Code, is invoked and made available, according to its terms, to the Secretaries of the military departments concerned, subject to the direction of the Secretary of Defense in the case of the Secretaries of the Army, Navy, and Air Force
this part lets him use military construction funds that haven’t been obligated yet.(allocated but not yet used). (for the simple folks this is like I am doing the house budget and put 50$ on the table for food, then you go and use 10$ for candy)
that the construction authority provided in section 2808 of title 10, United States Code, is invoked and made available, according to its terms, to the Secretary of Defense and, at the discretion of the Secretary of Defense, to the Secretaries of the military departments
As far as I can tell, the only thing I can find that would bother the states is that he is calling up the ready reserve without the states being able to say anything about it. If it were up to me as a judge, I would have to throw out the states claims as lacking standing.