Good question! I don't know of a database/list anywhere. I know California passed a law a couple-three years ago (or so) permitting motorcyclists to wear earplugs. Washington state doesn't allow them unless you have a perscription. Although the two times I've been pulled over in the last few years with them in, the officer never made any mention of them.
I did have a co-worker get a ticket on his HD for not having a litter bag though, so if you get an anal cop, anything is possible. (WA law states all motor vehicles must have a litter bag - and yes, you can get free ones from the state - the question is, where do you put it on a bike?)