The eigth amendment doesn't go as far as to define "cruel and unusual punishment" is. The nineth amendment doesn't define what rights should or shouldn't be protected.

Yes, there are some basic rights that are protected. But largely, the Constitution much more of a guideline about how the legal system should work than it is an absolute set of laws to be followed forevermore. Ambiguities are good in this case. Even if it did get Hamilton shot by Burr.