Any decree of a Roman Congregation is a good example of this. As stated in the book linked below, such decrees ordinarily require internal submission under pain of sin. If a learned man has a good reason for thinking something in it is false, he is not bound to assent internally, but cannot dissent from it openly. He cannot express to anyone his opinion that the decree is in error, without a grave sin of disobedience, temerity, and scandal; and he should be denied the sacraments while openly dissenting against such decrees.
I disagree with this and also, I am with SimpleMan, examples would be welcome.
If a decree of a Roman Congregation or a pope and council unambiguously teaches something binding, of course no one would deny submission, but since V2, look those who are waking up with what they consider to be good reasons to not agree with modern decrees. They are going to say something to someone. Whether they say something to a priest or to fellow trads, they owe it at least to themselves to question it if for no other reason than to correct themselves, no?
Prior to V2, except among heretics, this was not even considered an issue far as I know - "pay, pray and obey" was the reliable norm, but that norm was altogether ravaged in the 60s.