Before answering the questions that DGB and DF asked me, I will restate my idea in a different way. Very similar to John's words:
Just like the right to keep and bear arms is a warranty that you can defend yourself against a tyrannical state, abolition of the death penalty is the warranty that this tyrannical state won't be allowed to kill you.
Consider any tyranny, and you'll see that it resorts to death penalty.
The interdiction of death penalty should be written in the constitution (in any state: France, USA, etc…)