Reservatum ecclesiasticum

The reservatum ecclesiasticum (Latin, "ecclesiastical reservation"; German: Geistlicher Vorbehalt) was a provision of the Peace of Augsburg of 1555.

Such a realm was structurally Catholic, and its ruler was elected or appointed within the Church, having no hereditary rights.

The measure was contested in 1583, when the Archbishop-Elector of Cologne, Gebhard Truchsess von Waldburg, converted to Protestantism, specifically to Calvinism, and tried to retain his office.

The Spanish army, commanded by the Duke of Parma, physically recovered the electoral territory.

[3] In response, the Protestant Union's Assembly at Rothenburg ob der Tauber voted in March 1613 to not disband while the Catholic League was still in existence, and to ensure certain long-standing grievances were rectified, including the reservatum ecclesiasticum.