You need to be a constitutional lawyer to look at black letter law and say it is black letter law? Now I've heard everything.The implementation schedule was part of the law. the cited language does not permit any president to change the provisions that are written into the law.
the cited language allows a president to use executive orders to address things that are not written into the law, not to change things that are specifically included in the law.
the OP is wrong.
That is your claim. Are you a Constitutioinal lawyer?