Here is what John Paul II says in Ordinatio Sacerdotalis:
Wherefore, in order that all doubt may be removed regarding a matter of great importance, a matter which pertains to the Church’s divine constitution itself, in virtue of my ministry of confirming the brethren (cf. Lk 22:32) I declare that the Church has no authority whatsoever to confer priestly ordination on women and that this judgment is to be definitively held by all the Church’s faithful.
After he said this, people still quibbled as to whether this was something Catholics really had to believe. And so clarification was sought from the Congregation for the Doctrine of the Faith. Here is the question posed and the CDF’s response:
Dubium: Whether the teaching that the Church has no authority whatsoever to confer priestly ordination on women, which is presented in the Apostolic Letter Ordinatio Sacerdotalis to be held definitively, is to be understood as belonging to the deposit of faith.
This teaching requires definitive assent, since, founded on the written Word of God, and from the beginning constantly preserved and applied in the Tradition of the Church, it has been set forth infallibly by the ordinary and universal Magisterium (cf. Second Vatican Council, Dogmatic Constitution on the Church Lumen Gentium 25, 2). Thus, in the present circumstances, the Roman Pontiff, exercising his proper office of confirming the brethren (cf. Lk 22:32), has handed on this same teaching by a formal declaration, explicitly stating what is to be held always, everywhere, and by all, as belonging to the deposit of the faith.
The CDF explains their answer further here:
The issue has been settled. There can be no change. There will be no change.