Traditionalist Catholicism refers to a loosely-defined movement of Catholics who reject some or all of the changes made to Catholic liturgy and/or theology during the Second Ecumenical Council of the Vatican (or “Vatican II”), a massive gathering of church leaders that brought about dozens of sweeping reforms.
Traditionalist Catholics are best known to outsiders for their preference for celebrating Traditional Latin Mass rather than in the local vernacular. The largest of the Traditionalist Catholic societies is SSPX.
Some traditionalist Catholics reject the papal authority of Pope John XXIII (who called for the Vatican II council) or Pope Paul VI (the first post-Vatican II Pope), as well as their successors. This doctrine is called Sedevacantism, meaning “vacant seat”. As could be imagined, the Holy See denounces traditionalist Catholic organizations who espouse this belief, while other groups within the movement may enjoy full communion with Rome.
The Second Vatican Council represented the largest formal change to Catholic Church practices in centuries, and attempted to complete the “unfinished” work of the First Vatican Council, which had taken place a century prior. The stated goal of both Vatican Councils was to adapt the church to fit a changing world, combating emerging liberal tendencies in the secular world and paving a new way for the church to keep relevancy. Other changes were put into place in light of recent findings related to the early church in order to bring the Catholic Church closer to its roots. Some changes include:
- The encouragement of vernacular language for use in Mass, ending the use of Latin, which most laity didn’t speak or understand.
- The ability of laity to distribute the Eucharist.
- Ecumenical endeavors were encouraged in order to strengthen relations between the Catholic Church and other religious groups, including Protestant denominations. Protestants and Orthodox Christians were declared to be “separated brethren” of the church.
- The idea of Jews being referred to as an “accursed people” for their rejection of Jesus was denounced.
- Canon law and the Catechism were revised and rewritten (though this change took place very gradually).
- More freedom was given toward allowing contemporary music in worship, a change which notably brought about the use of guitars in church buildings.
- Marian devotions, while still fervently encouraged by the Church, were toned down in terms of formal reach, with many calls to devotion in churches being replaced with other practices. This was done in response to what was seen as “self-centered individualism” within the devotions, which was seen as superseding the communal nature of the liturgy.
- The liturgical calendar was altered, both in terms of dates and practice, with some minor holidays being removed.
- Some customs, such as abstaining from meat on Fridays or fasting prior to receiving the Eucharist, were abolished or made of lesser importance.
- More frequent participation in the Sacraments was encouraged.
Traditionalist vs. “Modernist” View
Most traditionalist groups view the Vatican II changes as liberalizing, with some going so far as to say they represent an abandonment of what it means to be Catholic, and/or signify a shift in the church toward protestantism. “Modernists” (non-traditionalist Catholics) tend to have the opposite view, seeing Vatican II as a reinforcement of Catholicism and a return to form.
Some traditionalists supportive of the Latin Mass have said that celebrating the mass in vernacular “strips it of its holy quality” and inspires doubt that Jesus is literally present in the Eucharist.
As mentioned above, “sedevacantism” denotes a tendency of some traditionalist Catholics to reject the authority of post-Vatican II Popes. A small handful of groups prefer to take this idea further by claiming to hold the “true” authority and electing “Popes” of their own, a practice which is called “conclavism”.
Conclavist claimants to the papacy can be viewed as modern day Antipopes, many of which have adopted the name “Peter II” (in reference to St. Peter, who is believed by Catholics to be the first pope), likely to illustrate a claim to represent a new beginning of sorts. Perhaps the most famous Conclavist is Pope Michael. Conclavist groups are a very small minority within the traditionalist movement, however. 
Growth in France
Like much of western Europe, the religious landscape of France tends to be highly secular and atheistic, with a growing presence of Islam. However, traditionalist Catholicism recently has seen a curious growth in France, with traditional Priests accounting for 20% of ordinations in 2018, and drawing in ire and concern from secular French leadership.
Many traditionalist Catholic groups operate schools and social pressure groups in France, such is the case of Civitas. These groups tend to operate in smaller towns and villages, but their influence can occasionally be wider.
Traditionalist Catholicism and Politics
Some traditionalist groups have had a political presence, whether intentional or unintentional. Traditionalists tend to espouse right-wing social views, and have been extensively slandered by the notoriously dishonest far-left Southern Poverty Law Center (SPLC) as a result, with the SPLC coining the term “Radical Traditional Catholicism” in reference to some groups, likely in order to make them seem more threatening.
As mentioned above, traditionalist Catholics in France operate pressure/protest groups which are opposed to secularism, homosexual “marriage”, abortion, etc. The influence of such groups can be seen in the efforts of mainstream or modernist French Catholics in recent years as well, with Catholicism.org writing in 2019 that Catholicism is visible in the French political landscape “for the first time in decades”.