Frederick Barbarossa sought to increase his authority in northern Italy (on the Lombard plain). The first step was to publish by announcing at a Diet at Ronçalia those of his rights which he intended to enforce. A war between Frederick and the Lombard followed. Its outcome is indicated by the peace treaty partially reproduced below.
The Diet of Ronçaglia, 1158
These are the rights of the crown:
Arimanniae [taxes paid by those who held special lands once owned by free
Lombards], public roads, navigable rivers and those which unite to form navigable rivers,
harbors, and the banks of rivers; tolls, coinage, profits from fines and penalties;
ownerless and confiscated lands, and the property of those who have contracted incestuous
marriages or have been outlawed for crimes mentioned in the Novellae of Justinian; rights
of conveyance [the right to demand conveyances of various kinds]on direct routes and
crossroads, and the prestation of ships [pressed into service to convey the emperor]; the
special taxes for the royal expedition; the appointment of officials for the
administration of justice; mines; royal palaces in the customary cities;
the profits of fisheries and saltworks; the property of those who are guilty of offenses
against the emperor; half the treasures discovered in places belonging to the emperor or
dedicated to religious purposes, and all of it if the finder was aided by the emperor.
The Peace of Constance, (January 25, 1183)
In the name of the holy and undivided Trinity. Frederick, by divine mercy emperor of the Romans, Augustus, and Henry VI, his son, king of the Romans, Augustus....
1. We, Frederick, Emperor of the Romans, and our son Henry...hereby grant to you, the cities, territories, and persons of the league, the regalia and other rights within and without the cities, as you have been accustomed to hold them; that is each member of the league shall have the same rights as the city of Verona has had in the past or has now.
4. The regalia which are not to be granted to the members of the league shall be determined in the following manner: in...each city, certain men shall be chosen for this purpose from both the bishopric and the city; these men shall be of good repute, capable of deciding these questions, and such as are not prejudice against either party. Acting with the bishop of the diocese, they shall swear to inquire into the questions of the regalia and to set aside those that by right belong to us. If, however, the cities do not wish to submit to this inquisition, they shall pay to us an annual tribute of 2000 marks in silver as compensation for our regalia. If this sum seems excessive, it may be reduced.
17. All injuries, losses, and damages which we or our followers have sustained from the league or any of its members are hereby pardoned, and all such transgressors are hereby received back into our favor.
18. We will not remain longer than is necessary in any city or bishopric.
19. It shall be permitted to the cities to erect fortifications within or without their boundries.
20. It shall be permitted to the [Lombard] League to maintain its organization as it now is or to renew it as often as it desires.
Source.
From Thatcher and McNeal, A Source Book for Medieval History (New York, 1905), p. 189-202.