The Constitution does NOT GRANT FedGov authority over murder. Murder comes under STATE jurisdiction. The Constitution grants FedGov authority over THREE crimes: Treason, Piracy and counterfeiting. That’s it and all. ONLY exception being murder in the military, which would fall under Congress’ authority to write rules governing military and naval forces. Sorry, you’re way out in LEFT field here, Chuck.
And rules of the road are at the STATE AND LOCAL levels ONLY. Congress has an obligation to provide Post Roads, true, but it has given the money to the States AND the authority to govern traffic on them.
You do know that we are talking about “government”, and not simply “federal government”, right?
And the courts have longed ruled that the federal government has a constitutional authority to try interstate crimes, including murder, in certain cases. I have not seen a strong libertarian push to eliminate all federal crimes from the criminal statutes, but I suppose there could be a few people who would argue that point. I’m just surprised to find one.