Quote:(e) The Attorney General shall promptly file a request with the U.S. District Court for the Central District of California to modify the Settlement Agreement in Flores v. Sessions, CV 85-4544 (“Flores settlement”), in a manner that would permit the Secretary, under present resource constraints, to detain alien families together throughout the pendency of criminal proceedings for improper entry or any removal or other immigration proceedings.

Sec. 4. Prioritization of Immigration Proceedings Involving Alien Families. The Attorney General shall, to the extent practicable, prioritize the adjudication of cases involving detained families.

Sec. 5. General Provisions. (a) Nothing in this order shall be construed to impair or otherwise affect:

(i) the authority granted by law to an executive department or agency, or the head thereof; or

(ii) the functions of the Director of the Office of Management and Budget relating to budgetary, administrative, or legislative proposals.

(b) This order shall be implemented in a manner consistent with applicable law and subject to the availability of appropriations.

I am not sure I agree with you. The court issued a mandate. This provision in the executive order says his administration will ask the settlement agreement to be modified. There may be a small window in which he is "making law," but that will immediately go away if the judge modifies her ruling and there would be no reason to see this as an unconstitutional EO. If the judge refuses to modify it, I would suspect that Trump will try to shift the blame to her, but he'd need to go back to separating families to be in compliance (again, then there'd be no reason to challenge this EO). If she stalls (which would be the political move is necessary for his EO to be challenged), then his EO will be unconstitutional. If she refuses and he continues to keep families together, he will be in violation of the law. 
Here is the reason given for challenging this executive order: 

Quote:Ferguson said the lawsuit brought by Washington and the other states will take the position that Trump's executive order is meaningless because it depends on passage of a Congressional appropriation that might not happen, as well as a judge's ruling to change the Flores decree.

"We do not think a judge is going to significantly alter that settlement," Ferguson said. 

Maybe I'm splitting hairs, but they are not saying it's unconstitutional because he's making law, but because it's depends on either a ruling from a judge or a congressional law to make it official. I would expect Trump to go back to doing things the way they were before, only this time he'll have a scapegoat, so to speak. In other words, it's a PR stunt if neither group acts, and he can absolve himself from not trying to do something about it, while claiming congress and the courts were being obstructionist.

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