On Friday, Google informed AdSense publishers and AdWords advertisers that they will begin allowing ads with gambling related themes in some cases.
Google told publishers:
Beginning on September 27, we're expanding the inventory of Google ads eligible to show on the AdSense network to include gambling-related ads from trusted advertisers.
Google clarifies some of the limitations saying it depends on the gambling site, the user's location and so on. Google said:
Please note that the AdSense program policies will continue to prohibit the placement of ads on sites that accept money or allow users to place bets in exchange for an opportunity to earn cash or other prizes, directly from the site. In addition, these new ads will only be shown to users in regions where gambling is legal, which is determined by the location of the end-user. A full list of these locations can be found at the following link. Finally, publishers may not opt in to receiving ads from this new category if their sites are intended for individuals under 18 years of age.
Finally, the only way to see gambling ads on your site is to opt into it. Otherwise, at this time, Google will not show the ads. To opt in, read these instructions.
For more on the AdWords side see this link.