Libertas ecclesiae ("freedom of the Church" in Latin) is the notion of freedom of ecclesiastical authority from secular or the temporal power, which guided the Reform movement which began in the 11th century. It is also the name of a papal bull issued by Gregory VII in 1079.
After the decentralization of the post-Carolingian period, this became the slogan of the Church in light of disapproval over lay warlords installing themselves as abbots and other high-profile churchmen. Unfit to perform theological functions, much less to defend the interests of the Church, these warlords viewed Church property as an extension of their own landholdings.
What resulted was the plunder of movable wealth (of which the monasteries had become the keepers during the period of Viking invasion) and the parcelling out of land and office as the temporal powers saw fit. This sorry state of the Church prompted enthusiasm for 'freeing' it from the direct control of these milites; Gregory VII helped frame this goal through the specifics of his reform program.
In addition to calling for spiritually pure figures at the helm of the Church, Gregory VII addressed the practical problems of pluralism (holding more than one church office) and poorly educated clerics.