This article sadly makes it a lot clearer:
http://www.ogpaper.com/news/news-0283.html
“What does this mean? It means that, if a state has a law prohibiting casino gambling at that state, online casinos cannot operate in that particular state, even with a license. And in the United States, there are only 11 states which have private casinos (except Indian tribal gambling, which is treated separately). So in the other 40 states, where casino gambling is illegal – online casinos cannot operate. And when those 11 states already have laws or are working on laws to explicitly prohibit online gambling – there are no states left where a licensee could operate – thus banning online gambling on a state level.”