Correct me if I'm wrong. The difference between you and I in this discussion is that you find "the law" to be legitimate, properly flowing from the consent of the governed. That sort of "respect" as opposed to "respect" for the Mafia or the Nazis or MS-13 on account of their superior firepower.
I think you and I are likely to agree on what Congress and the courts say, after all, they more or less provide direct assertions. The federal government, supported by SCOTUS in the Raich decision, has assumed the power to bring federal criminal charges for possession of pot. Similarly, Congress has modified the "no guns in a school zone act" so that it is the exercise of a judicially-endorsed constitutional power of the federal government.
What isn't clear is whether or not you and I are in agreement that these assertions of federal power, by Congress and the federal courts, deserve moral respect. I find them ultra vires.
And no, I don't think our government deserves moral respect. Government, to me, is no different than organized crime. They force you to pay tribute, in order to protect you from other criminal organizations. And they require you to do their bidding or else suffer the consequences. How is that different than the mafia?
As for what is or isn't beyond their power, the question is a circular one, because the "geniuses" who wrote the Constitution left the inmates in charge of the asylum. At best we have branches checking each other, but no check when all are on the same page. If the Congress says it's OK, and the president agrees, and the SCOTUS agrees, that's that. What I personally think has no relevance.