Just because something isn't a law of the universe doesn't mean it isn't real. English is an essentially arbitrary set of rules and sounds, yet I am using it to transport my thoughts into your head, where if I used my own fake words instead we'd glarf bort tinp ko esag.

Or, more on point, there's a world of difference between "won't necessarily protect you" and "definitely won't protect you", where sovereign citizen bullshit is squarely in the latter category.