If somneone is old and sick and they want assisted suicide, it is against the law. This does not apply to issues where someone wants them to "pull the plug" so to speak, which is merely the refusal to allow heroic and futile efforts to keep someone alive.

As for the death penalty, as you point out, it is also the law of the land, and because it is, being old and sick should not be a reason to stay execution. I suspect some lawyer thought this one up for the guy in California as a last ditch way to save him. Obviously it didn't work.

So overall there is no real conflict here.