Myths of the Norsemen From the Eddas and Sagas
“Glitner is the tenth;
It is on gold sustained,
And also with silver decked.
There Forseti dwells
Throughout all time,
And every strife allays.”
Sæmund’s Edda (Thorpe’s tr.).
Here, upon an exalted throne, Forseti, the lawgiver, sat day after day, settling the differences of gods and men, patiently listening to both sides of every question, and finally pronouncing sentences so equitable that none ever found fault with his decrees. Such were this god’s eloquence and power of persuasion that he always succeeded in touching his hearers’ hearts, and never failed to reconcile even the most bitter foes. All who left his presence were thereafter sure to live in peace, for none dared break a vow once made to him, lest they should incur his just anger and be smitten immediately unto death.
“Forsete, Balder’s high-born son,
Hath heard mine oath;
Strike dead, Forset’, if e’er I’m won
To break my troth.”
Viking Tales of the North (R. B. Anderson). 
As god of justice and eternal law, Forseti was supposed to preside over every judicial assembly; he was invariably appealed to by all who were about to undergo a trial, and it was said that he rarely failed to help the deserving.
The Story of Heligoland
In order to facilitate the administration of justice throughout their land it is related that the Frisians commissioned twelve of their wisest men, the Asegeir, or elders, to collect the laws of the various families and tribes composing their nation, and to compile from them a code which should be the basis of uniform laws. The elders, having painstakingly finished their task of collecting this miscellaneous information, embarked upon a small vessel, to seek some secluded spot where they might conduct their deliberations in peace. But no sooner had they pushed away from shore than a tempest arose, which drove their vessel far out to sea, first on this course and then on that, until they entirely lost their bearings. In their distress the twelve jurists called upon Forseti, begging him to help them to reach land once again, and the prayer was scarcely ended when they perceived, to their utter surprise, that the vessel contained a thirteenth passenger.
Seizing the rudder, the newcomer silently brought the vessel round, steering it towards the place where the waves dashed highest, and in an incredibly short space of time they came to an island, where the steersman motioned them to disembark. In awestruck silence the twelve men obeyed; and their surprise was further excited when they saw the stranger fling his battle-axe, and a limpid spring gush forth from the spot on the greensward where it fell. Imitating the stranger, all drank of this water without a word; then they sat down in a circle, marvelling because the newcomer resembled each one of them in some particular, but yet was very different from any one of them in general aspect and mien.
Suddenly the silence was broken, and the stranger began to speak in low tones, which grew firmer and louder as he proceeded to expound a code of laws which combined all the good points of the various existing regulations which the Asegeir had collected. His speech being finished, the speaker vanished as suddenly and mysteriously as he had appeared, and the twelve jurists, recovering power of speech, simultaneously exclaimed that Forseti himself had been among them, and had delivered the code of laws by which the Frisians should henceforth be judged. In commemoration of the god’s appearance they declared the island upon which they stood to be holy, and they pronounced a solemn curse upon any who might dare to desecrate its sanctity by quarrel or bloodshed. Accordingly this island, known as Forseti’s land or Heligoland (holy land), was greatly respected by all the Northern nations, and even the boldest vikings refrained from raiding its shores, lest they should suffer shipwreck or meet a shameful death in punishment for their crime.