Kicking back a law because it's constitutionally not the business of government to have laws that say that, is very different than kicking back a law because while it is something upon which legislation could constitutionally be had, and the executive is acting in accordance with the law as written, the judiciary doesn't like the way in which the legislature chose to phrase how it delegated authority... that's a different story.

Executive agencies aren't a "fourth branch of government with little oversight", they're article II section 2 'departments' of the executive, established by law, and controlled by the president and appointed officers, with as much oversight as congress legislates to require, plus accountability to the courts for remaining within the bounds of their legal and constitutional authority.