Did you ever show that copy to the police that stopped you?
It's not really important to me, but I have read discussions on this subject in different forums where members have researched their own state laws and/or updated info on the federal law, found conflicting info, and posted links to it.
Modulating headlights certainly work and believe using them is a personal choice.
I had a Barney Fife type stake out my appartment when I was working a temperary job in Oregon because I had out of state tags.
The legals at work advised me that I did not need Oregon tags, I checked with the Oregon DMV and they confirmed it, so I asked them for a letter or something to show Barney Fife.
Answer: "We don't issue get out of jail free cards, if you get a ticket, go to court and tell the judge your situation."
...I got Oregon tags, after paying for/passing an emissions test:redface:
Ken