Prosciption for anyone with a net worth over a billion dollars. It becomes an affirmative defense in a murder trial that the victim had wealth beyond the legal maximum. This avoids the issue of government enforcement. You don't have to try and track down every criminal billionaire squirreling their wealth away in hidden accounts. It just becomes legal to kill anyone with a net worth over a certain amount. The government doesn't have to track down and arrest billionaires. They have to worry about their own children killing them, inheriting their money, and just donating anything over the legal threshold.