While there is considerable opposition to the death penalty in certain sectors of the Church, including, apparently, the Pope, it's still legitimate. Much of the opposition, actually, is from left-wing clergy who are covertly in favor of abortion and use the death penalty issue as a way of attempting to delegitimize the anti-abortion movement. It's called the "seamless garment" - meaning that if you're opposed to abortion, you also have to be opposed to the death penalty, ignoring the difference between an innocent unborn child and, say, a cold-blooded mass murderer. And ignoring the fact that abortion IS forbidden by the Church, without any ambiguity.
I was very glad that Scalia said what he did. A judge who doesn't want to impose this penalty should excuse himself from death penalty cases. It's time to discuss this matter openly.