The executive branch cannot define the law or interpret the law.
That is exactly what the Executive branch is tasked to do.
Justice Department belongs to the Executive branch.
Under direct control of the President.
Prosecutorial Discretion belongs to the Executive.
Judicial determines if the executive decision it true of false.
Also, this gripe that the President is not following foreign policy . . .
The President sets Foreign Policy.
It is impossible for a President to circumvent foreign policy.