I don’t think it does. Discretion is fundamentally case by case. Drawing categorical lines is legislative.
It’s akin to the distinction between law and equity courts at common law.
Stepping back, both doctrines (non delegation, unitary executive) are fundamentally about the courts overstepping. If both houses of Congress pass a law creating an agency with a director that can only be fired for cause and the president signs it, the Supreme Court should stay out of it.
Enacting legislation is very difficult, the presumption of constitutionality should be taken more seriously.
> Drawing categorical lines is legislative.
That’s even worse. If that’s the case, Congress must adopt those exemptions by law. It can’t delegate lawmaking powers to its employees.
> Stepping back, both doctrines (non delegation, unitary executive) are fundamentally about the courts overstepping
Unless you toss out the concept of judicial review altogether, policing the structural rules of the constitution is exactly what the courts should be doing. The courts have no say about the merits of Congressional acts. But they should review whether Congress has allocated powers to various entities in a way that’s consistent with separation of powers.
That’s too high a level of generality. Sure police situations where the branches are at direct loggerheads.
But in this case we have a law passed by congress and signed by the president. There’s no need to step in, the ordinary political processes are more than sufficient. If the new President and congress doesn’t like what the last ones did they have the exact same tools at their disposal to undo it.
Let them play!