Q. 1. What is the "Gallicanism" heresy?
A. 1. The "Gallicanism" heresy is the belief that the head of the state/country's authority is equal to that of the Pope.
"Gallicanism" is a form of Anglicanism where the head of the country rules over the Church.
This heresy was condemned by pope Pius IX's Syllabus of Errors, by pope Leo XIII's Encyclical Immortale Dei, and by the first Vatican Council.