George Weigel thinks it was ‘correct‘ to drop the Atomic Bomb on Hiroshima and Nagasaki. The Second Ecumenical Council of the Vatican, in contrast, teaches that,

[T]his Holy Synod adopts the condemnations of total war which have already been uttered by recent popes, and declares: Every operation of war which aims indiscriminately at the destruction of whole cities, or of widespread areas with their inhabitants, is a crime against God and humanity itself which is to be firmly and unhesitatingly condemned.

– Gaudium et spes 80

Luckily for Mr Weigel, Pope Paul VI clarified in 1966 that, “In view of the pastoral nature of the Council, it avoided proclaiming in an extraordinary manner any dogma carrying the mark of infallibility.” So that means that the definition quoted above belongs to the secondary object of the magisterium of which Canon 750§ 2 tells us,

…each and everything set forth definitively by the Magisterium of the Church regarding teaching on faith and morals must be firmly accepted and held; namely, those things required for the holy keeping and faithful exposition of the deposit of faith; therefore, anyone who rejects propositions which are to be held definitively sets himself against the teaching of the Catholic Church.

So, Mr Weigel is not teaching heresy, only error. In its Doctrinal Commentary on the 1998 Apostolic Letter (Motu Proprio) Ad Tuendam Fidem the CDF tells us “Whoever denies these truths would be in a position of rejecting a truth of Catholic doctrine and would therefore no longer be in full communion with the Catholic Church.”

The Code of Canon Law (1983) goes on to say,

Canon 1371 – The following are to be punished with a just penalty:

1° a person who, apart from the case mentioned in canon 1364 § 1, teaches a doctrine condemned by the Roman Pontiff, or by an Ecumenical Council, or obstinately rejects the teachings mentioned in canon 750 § 2 or in canon 752 and, when warned by the Apostolic See or by the Ordinary, does not retract

We can only hope that the Apostolic See will soon warn Mr Weigel so he can return to “full communion with the Catholic Church.”