According to Canon Law, a Catholic owes "religious submission of the will and intellect" to the authentic exercise of the ordinary magisterium.
Specifically to the authentic, non-definitive teachings of the Church's ordinary magisterium.
But what Does "Religious Submission of the Will and Intellect" Mean?
It means Catholics must approach such teachings with an open and respectful attitude, rather than a critical or defiant spirit.
And what is an authentic exercise of the ordinary magisterium?
Does it have to be in continuity with scripture and Tradition?
Yes, by definition, the Magisterium is strictly bound to continuity with Scripture and Tradition.
As the Second Vatican Council formally declared in Dei Verbum (Paragraph 10):
"The Magisterium is not superior to the Word of God, but is its servant. It teaches only what has been handed on". Because its sole purpose is to guard, interpret, and explain the pre-existing "Deposit of Faith," an authentic exercise of teaching cannot invent completely new or fundamentally contradictory doctrines.
The exact, official Vatican English translation of Canon 752 reads as follows:
"While the assent of faith is not required, a religious submission of intellect and will is to be given to any doctrine which either the Supreme Pontiff or the College of Bishops, exercising their authentic magisterium, declare upon a matter of faith or morals, even though they do not intend to proclaim that doctrine by definitive act; Christ's faithful are therefore to ensure that they avoid whatever does not accord with that doctrine."
So if the modern Church were to declare an ancient hope--held by ante Nicene and post Nicene Fathers, ordained Saints and Doctors of the Church, by some within her bosom to this very day (and hinted at in Holy Scripture itself) a heresy, would that be an "authentic" exercise of the ordinary magisterium?
I believe Fr. Waclaw Hryniewicz suggested otherwise here.
Universal hope is the duty of every Christian. Traditional eschatology perceives only two ultimate possibilities: heaven or hell. It does not take into account the great synthesis of the history of the world in God. It also excludes all thoughts about the universal reconciliation of the lost creatures with God. It does not hear the voice of hope resounding in numerous biblical statements, nor does it heed the patient cry of hope which has not vanished from Christianity throughout the ages.
--Fr. Wacław Hryniewicz OMI, "Universal Salvation: Questions on Soteriological Universalism," in Polish Philosophical Studies VII: Universalism: Past and Present (Washington, D.C.: Council for Research in Values and Philosophy, 2007), p. 61.
I also believe this statement from Cardinal John Henry Newman (regarding the 4th century Arian crisis) is worth noting.
It is not a little remarkable, that, in the fourth century this consensus of the faithful was the voice of the Infallible Church. In that time of immense confusion the divine dogma of our Lord's divinity was proclaimed, enforced, maintained, and (humanly speaking) preserved, far more by the Ecclesia docta (the learned church) than by the Ecclesia docens (the teaching church); the body of the episcopate was unfaithful to its commission, while the body of the laity was faithful to its baptism.
--John Henry Newman, "On Consulting the Faithful in Matters of Doctrine," Note 5, The Arians of the Fourth Century (London: Longmans, Green, and Co., 1890 edition), pp. 445-446.
Note: In other words, learned lay members of the church were right (at that time) to openly and vocally dissent from what was being taught by the bishops of the Church, because what was being taught was not an authentic exercise of the ordinary magisterium.