The source of the "contagion", as French…
October 1555 CE
The source of the "contagion", as French court pamphleteers put it, is ever Geneva, where the former Frenchman John Calvin achieves undisputed religious supremacy in 1555, the very year that the French Reformed Church organizes itself at a synod under the king's nose, as it were, in Paris.
At the Peace of Augsburg signed in September in Germany, the essential concept is cuius regio eius religio, "Whose region, his religion".
In other words, the religion of the king or other ruler would be the religion of the people.
The petty princes of Germany are enabled to dictate the religion of their subjects, and it comes to be sensed as a mark of weakness that the King of France cannot do so: "One King, One Faith" is to become the rallying cry of the ultra-Catholic party of the Guise faction.
The Parlement de Paris is deeply divided on the issues.
When the King approaches the Parlement for its formal advice beforehand on the best means of punishing and stamping out heresy, the moderate voices of président Pierre Séguier and conseiller du Drac urge against the proposed new edict (as unnecessary) and specifically oppose the introduction of an Inquisition into France, an innovation that would appear to circumvent the king's justice, vested in the parlement.