Word meaning the act of the state taking away one's right to live

You might want to consider using attaint (to pass judgment of death or outlawry upon) or attainder (the extinction of a person's civil rights resulting from a sentence of death). These aren't very common words, they're legalistic and they're both rather archaic. But I believe they mean almost exactly what you intend to convey.

Are you thinking of forfeiture of life? See this article entitled, "The Death Penalty and the Forfeiture Thesis" Here is an excerpt:

Death penalty retentionists often attempt to counter this argument by asserting that persons convicted of capital crimes have forfeited their right to life.

I'm not sure if this is an act of the state, though. It is more that, by their actions, those who commit capital crimes do the forfeiting.

Maybe outlawry? (Although declaring someone an outlaw was broader than your definition - it meant that not only the state, but anyone, was entitled to kill the person.)

Closest one I have found so far is ...Dispossession ... a biblical worldview that was framed in the constitution are right given by God that we inherently possessed ..so I think that would fit within the definition of it ...