US law question

Hi,
Anyone knows if I am allowed to use incentive offers as a "ticket" for people to enter a prize draw? It is probably illegal to ask for money, like in almost every country.. but howabout using email submits?

So people would fill out an offer to be able to win something bought and shipped by me? (I guess this is pretty straightforward to see why I'm asking)

Lismos

I heard BBC case