I agree that Congress has no power to regulate our lives - in areas like education and farming, etc, where the constitution doesn't given any "enumerated" authority to the feds to act. But the federal constitution DOES protect certain rights - like right to property, right to speech, religion= --- and not to be deprived of life without due process; in protecting constitutional rights, the federal government DOES have a role - - and it can override the states if the states are abridging constitutional rights.
BIG difference.
It is illogical to think that the constitution protects the life of death row criminals exclusively. These provisions protecting due process in taking the life of criminals are provisions that present the extreme case. If the extreme case gets these protections, then certainly innocent citizens are guaranteed these rights as well. Otherwise, the constitution is a preposterous document.
And, if the constitution is protecting the death row criminal with this blanket statement and does not say specifically that it is an issue delegated to the states, then it is an issue enforceable on a national level.