If you know of specific cases, please e-mail or PM that to the moderators.
Discussing specific cases here in the forum is not a good idea because if someone isn't an illegal dealer but you brand them as such, you will have damaged their reputation. And since you wouldn't want someone leveling accusations publically against you, I'm sure that you wouldn't want to do that to them either.
But please do e-mail or PM the moderators. Include any specific cases or other information you have.