Jerry, it is instructive to note that in the UK, the powers the executive gets via delegation from the legislature are called “Henry VIII Powers,” after the monarch who strong-armed Parliament into starting off this practice. I suspect it is one of those practices the Founding Fathers found so abhorrent that they saw no need to prohibit it in the Constitution, as no self-respecting American legislature would do it. Unfortunately, now when we need it spelled out constitutionally it is exactly the time when such an amendment would have no chance of success, so useful does Congress find the practice.