Phil,
By coincidence, I stumbled on an article in a recent mag concerning safety requirements and state's requirements. The headlight laws in the US vary by state. Nearly all require headlight usage under one or more of the following guildlines;
1. If equiped w/ permanently wired headlights
2. All bikes after a particular date - Those dates were generally mid '70s to 1980.

Six states have NO requirement. I don't remember them all but I think some were Ala. Alaska, Ill.

If I can remember to look, I'll post the mag name and issue. Maybe those interested can use it as a reference.

There's a lot of variation on the requirements that those traveling from state to state may find helpful - stuff from helmet laws to handle bar heigth, to passenger seating, etc.