Guys, gambling has been illegal or partially legal or whatever mix of stuff for always in various states.
Here is a summary:
xhttp://www.gambling-law-us.com/State-Law-Summary/
This is not federal law, the United Sates has no law about internet gambling as of yet.
Make sure you pay attention to the internet applicable section. Gambling laws are diverse and confusing.
The fact that internet gambling itself is illegal does not affect advertising. Advertising falls in the US under the free speech law.
The only state that has a law now that threatens advertising is Washington.
Do not target people who live in paces where gambling online is illegal. Carry a disclaimer. Make it visible.
Of course I am not a lawyer and what I have to say may be utter nonsense and for your entertainment only.