As Rolf Hendrik Bremmer, Jr., notes in his introduction to the Old Frisian text, this is a legend about the origins of Frisian law that combines both Christian and pre-Christian elements. I’ll include notes and links that may be of further assistance. Modern Heathens, of course, remember King Redbad as the Frisian hero who refused to convert right before he was to be baptized. “King Karl” is often rendered as Charlemagne in English translations of the title of this section of the Codex Unia. However, it would make far more sense for the story to actually be about Karl Martel and Redbad, with elements from an earlier, pre-Christian legend carrying through.
While the stranger who suddenly appears at sea and gives the Frisians their law is not identified, some of us do presume this to be a surviving tale about Fosite (Forseti).
PART I – KARL AND REDBAD
Concerning King Karl and Redbad
Then King Karl and King Redbad came to this land from Denmark, each with a band of soldiers, and told the other that the land was his. They wanted to reconcile their wise people, and their armies wanted to fight. Nonetheless, the men decreed that they would reconcile if the two kings called for an “ordeal by standing still” so that one might win. [FN1] Then the armies gathered together and they stood through an entire period of 12 to 24 hours.
Then King Karl let his glove fall; King Redbad reached for it. [FN2]
King Karl said, “Ah ha! Ah ha! This land is mine!” and he laughed. Therefore, his dwelling mound is called “Hachense.” [FN3]
“Why?” asked Redbad.
Then Karl said, “You have become my vassal.”
And Redbad said “Oh, woe!” Therefore, his dwelling mound is called “Wachense.” [FN4]
Then King Redbad left the land and King Karl wanted to sit in judgment. But he could not, because the free land was so full that there was no place to hold court. [FN5] Then he sent a messenger to the Seven Sealands [FN6] to find a free place to hold court. He bought it with treasure/cattle and Danish shillings. He set up court, summoned the Frisians before him, and ordered them to choose their law.
[FN1] Rolf H. Bremmer, Jr., further explains that this ordeal involved standing motionless with the arms stretched sideways. See Rolf H. Bremmer, Jr., An Introduction to Old Frisian, 176 (2009).
[FN2] Per the author’s note on page 176, “[p]resenting a gauntlet was a common ritual to symbolize the acknowledgment of a liege lord.”
[FN3] This site is allegedly nearby the modern capital of Friesland, Leeuwarden (Ljouwert). Hach means “high” in Old Frisian. I am not entirely sure if the name derives from that word, or from the verb “to laugh,” hlakkia.
[FN4] Wach! is Old Frisian for “Woe!”
[FN5] The original word is thingia meaning “to proceed, sue, administer justice, or sit in judgment,” a cognate that appears in other Germanic languages.
[FN6] The “Seven Sealands” show up in modern usage as well. They are the lands that traditionally make up the Frisian areas along the North Sea. On the modern flag of Friesland (a province in the Netherlands), the Seven Sealands are symbolized by red, heart-shaped lily blossoms.