It has the tacit consent of Congress, so it's mostly only illegal in the way it's carried out. Congress could make most of it legal right now, but they don't want to put their names on it. Some of it would probably be unconstitutional for Congress to authorize (ironically via the nondelegation clause which is now being repurposed to justify a thoroughly unconstituational unitary executive arrangement), but much of it would not be, so it's de jure illegal but de facto legal.

At a certain level legality is enforcement. If the enforcers of the rules decline to enforce them, you're better off acknowledging what is and dealing with it.