Mark,
I don't think it was an age thing, unless there are a lot of bald kids running around buying powder! This wasn't when I was paying for it, this was just to have it handed to me from the safe behind the gun counter. I've bought Pyrodex here in MD at several places, never needing to be kept "on file", so I don't think it was a MD law. I just got into reloading, and I'll be going there to get some H4350 powder this week, so I'll ask a few more questions about the policy.
Charlie