I don't understand how the POTUS has the unilateral power to do this. And is it clear that he does? If not, I see another SCOTUS case on the horizon.
You're the lawyer, but that seems tough to me - SCOTUS, across its normal left-right cleavage, normally sides with the executive's discretion to choose which cases to prosecute. And the administration is just declining to prosecute here, not creating any new visa categories.
Here, for example, is Scalia on the "deferred action" mechanism being used here in
Reno v. American-Arab Anti-Discrimination Committee. (Two separate passages, separated by my ellipsis).
