Google no longer accept gambling related ads from any country, i’m from the uk and tryed to get an ad approved tragetting uk visitors only because gambling is legal here and they said they don’t accept any gambling related ads. The ones you see listed are probaly using a way to get listed which exists which goes round google’s detection system, there is a way but you’ll get taken down when once google checks your site, no one is going to tell you the way i’m afraid.