I'd never heard of them before. Apparently, they have their fair share of "nuts".
Here's a
link with a little more information, keeping in mind it's from CBS and, therefore, inflammatory.
This part, from the beginning, is interesting --
(CBS News)
This is a story about a group of Americans you've likely never heard of: they're called "sovereign citizens." Many don't pay taxes, carry a driver's license or hold a Social Security card.
--- inasmuch as that partially describes the Amish.