You had an extra d at the end in your link.
Interesting, but don’t know quite what to make of it - esp since it gets into some kind of a Jesuit conspiracy spiel.
Through usage and custom, horizontal stripes had become adopted for use over military posts, and vertical stripes adopted for use over civilian establishments. The Civil Flag, intended for peacetime usage in custom house civilian settings, had vertical stripes with blue stars on a white field. By the Law of the Flag, this design denoted civil jurisdiction under the Constitution and common law as opposed to military jurisdiction under admiralty/military law.
Here is a good link, fixing the extra 'd':
https://www.michiganfreedejurestate.us/files/HISTORY_OF_THE_US_CIVIL_FLAG.pdf
It is my understanding that all civil courts today in the US operate under *Admiralty law*. But, I'm no lawyer, just play one occasionally on FR...