The Edict of Restitution, passed eleven years into the Thirty Years' War on March 6, 1629 following Catholic successes at arms, was a belated attempt by Ferdinand II, Holy Roman Emperor to impose and restore the religious and territorial situations reached in the Peace of Augsburg (1555). From the pro-Catholic viewpoint, the "Ecclesiastical Reservation" of the Augsburg treaty had impeded the secularization of Catholic lands after 1555, so no further Catholic lands could be converted to Protestant control. However, over several decades of weak willed emperors the "Ecclesiastical Reservation" had not been enforced against the encroaching Protestants.
In 1635 the Edict of Restitution was effectively revoked, with the terms of the Peace of Prague
While Ferdinand II was on his deathbed in September of 1634, his son Ferdinand III persuaded him to revoke the Edict of Restitution. That was something only the Holy Roman Emperor could do, and Ferdinand III knew that if there was ever another one, it was unlikely that it would be him.