Cardinal Ratzinger on capital punishment and just war

"Not all moral issues have the same moral weight as abortion and euthanasia. For example, if a Catholic were to be at odds with the Holy Father on the application of capital punishment or on the decision to wage war, he would not for that reason be considered unworthy to present himself to receive Holy Communion. While the Church exhorts civil authorities to seek peace, not war, and to exercise discretion and mercy in imposing punishment on criminals, it may still be permissible to take up arms to repel an aggressor or to have recourse to capital punishment. There may be a legitimate diversity of opinion even among Catholics about waging war and applying the death penalty, but not however with regard to abortion and euthanasia."

(Worthiness to Receive Holy Communion, General Principles - sent by Cardinal Ratzinger to Cardinal McCarrick, Archbishop of Washington, D.C., and made public in July, 2004, n. 3)