Is a presidential executive order permanent law?
It is generally legally binding if it is focused on legitimate things E.O.s are supposed to address. Even then, the next president can nullify, or change them with a new E.O.
A president can’t unilaterally issue an edict like DACA. That is the business of the U.S. Congress. Congress Legislates.
Neither the Executive Branch of the SCOTUS is authorized to legislate.
Trump saw things differently concerning DACA, and began a process to end it or force Congress to pass legislation making it a legal program.
I personally hope they don’t.
An executive order can nullify another.
It’s an order not a law. I can see challenging positive orders that may transcend past the Executive Branch and skirt into violating division of powers with States, but how in the heck is a Judge going to explain overruling an Executive Order of a negative?