Catholics who feel called to seek abolition of capital punishment should do so in a way that respects the Constitution of the United States. This is the point of an article I have in the most recent issue of First Things, which is available here (behind their paywall). For those who are interested, here is a summary of the argument.
Opponents of the death penalty will of course be tempted to get rid of it by the easiest, most convenient way. And in our highly litigious culture, one obvious way that presents itself is trying to get the Supreme Court to declare it unconstitutional. This temptation is not unique to opponents of capital punishment, of course. It is a temptation that all politically active Americans encounter, from conservatives who want the Court to declare the Affordable Care Act unconstitutional to the proponents of same-sex marriage who want the Court to declare it a constitutional right (and who recently succeeded).
And sometimes, of course, it is OK to follow this temptation. After all, some laws really are unconstitutional, or are arguably unconstitutional. If you think you are up against one of this description, there is nothing wrong with taking it to court.
The temptation should be resisted in the case of capital punishment, though, because a victory there could only be won at the expense of the rule of law–and that is too great a cost. Some things are clearly unconstitutional, and some things are arguably unconstitutional. Capital punishment does not fall into either of those categories. It rather falls into the category of things that are unarguably constitutional.
Those who seek abolition of capital punishment by means of constitutional interpretation contend that it is a violation of the Eighth Amendment, which forbids punishments that are “cruel and unusual.” The problem with this approach is that elsewhere in the text the Constitution explicitly contemplates death as a lawful punishment. The Fifth Amendment (and the Fourteenth) provide that government may not deprive anyone of life, liberty, or property without due process of law. This is the same thing as saying that the government may deprive you of life with due process of law–meaning if you are duly convicted of a serious crime. The Fifth Amendment similarly refers to “capital” crimes–meaning crimes for which you could get capital punishment.
An interpretation of the Constitution that not only goes beyond the words but actually goes against the words is no longer really an honest interpretation but is instead a court just doing what it wants and using the Constitution as a cover for it. This is in fact lawlessness, and we should not encourage it, even if we do so in a good cause.
Besides, Catholics–like all Americans–still have a lot to protect–like the free exercise of religion–by respecting the Constitution’s clear meaning.