If I read the SCOTUS ruling correctly they returned it to the state legislatures not the State or Federal legislature.
I think that means that a constitutional challenge to federal legislation will be upheld by the court as a violation of state’s rights.
To enact it at the federal level will take an admendment.
A Republican President and a Republican Congress can not prevent a state from punishing a person who kills a Democrat.
The federal government can do whatever they want with the commerce clause.
And on top of that, such an amendment would entail an attack on the Bill of Rights.