When Pope Pius V excommunicated Elizabeth I of England in the 16th century, he also issued a plenary indulgence to anyone who assassinated her and delivered the country back into the Catholic Church.
Given that the Pope teaches infallibly on matters of doctrine and morals. And that whether it’s acceptable to kill another human being is certainly a matter of morals. Does that mean that this offer still stands? Would the current Pope be bound to honour the indulgence if someone, in good faith and in an attempt to re-Catholicize England, was to assassinate Elizabeth II? Can the Pope rescind this and apologise for it? Would that mean that it was wrong at the time, or just that it would be wrong now?
FYI, I am not planning to assassinate the Queen, I just want to know whether the Church still thinks it was right to issue an indulgence like that? If so, that is rather worrying.