Regnans in ExcelsisRegnans in Excelsis was a Papal bull issued on February 25, 1570 by Pope Pius V declaring Elizabeth I to be a heretic and releasing all her subjects from any allegiance. It also declared any follower of Elizabeth excommunicated.
The bull opened the way for any Catholic to attempt an assassination, and provoked the English government into taking more repressive actions against the Jesuits whom they feared were acting in the interests of Spain and the Papacy.
In order to relieve the pressures on English Catholics, and to conceal the genuinely subversive nature of the bull, Pope Gregory XIII issued a clarification in 1580, explaining that Catholics should obey the Queen in all civil matters, until such time as a suitable opportunity presented itself for her overthrow. In the Spanish Armada crisis, it transpired that most of the Catholics resident in England remained loyal, and that the real threat to the throne consisted of those like Cardinal William Allen and Robert Parsons who were already exiles.