The law is whatever the local LEO who has pulled you over decides it is. Try invoking your rights and he’ll magically find an eight-ball of cocaine under your seat. Why do you think they are all paranoid about civilians filming their arrest stops?
No, it appears I was breaking the law and didn’t even know it:
http://corpslakes.usace.army.mil/employees/cecwon/memos-drill.cfm?Id=789
Bummer. Won’t make that mistake again. I’m just glad the local LEO was cool.