That's all nice and well, but then the person killing the killer should forfeit their right to live also... My point is this: We no longer live in a society where nature can kill you at any opportunity with little warning. Our society discusses and debates. While I understand the feeling behind the sentiment, it does little to create harmony. Another point is that if you look at the animal kingdom, there is no concept of an eye-for-and-eye. The Lion killing an Antilope does not get set upon by the family of the Antilope.

Only if that is the contract that has been made. Different contracts are possible.

For example, we can all make a contract with society to perpetuate a better society, and in return receive help from society. Someone who breaks that contract has forfeited the right to support, but noone is charged with killing them.

Such a contract does not imply communism; it simply requires that we individually reward good character.