This one’s crucial:

“In 1210, Pope Innocent III required of the Waldensian heretics, as one of the conditions of their reconciliation with the Church, that they affirm that the death penalty can ‘without mortal sin’ be inflicted. Now, the Waldensians had claimed that ...

“ ... the Gospel requires Christians to refrain from violence and from punishing evildoers. It was their interpretation of the higher demands of Christian morality, specifically (as opposed to natural law), that motivated their opposition to capital punishment ...

“ ... Pope Innocent, then, was essentially rejecting as heterodox this interpretation of the demands of the Gospel.”

~ Edward Feser https://www.catholicworldreport.com/2018/01/20/capital-punishment-and-the-infallibility-of-the-ordinary-magisterium/