Businesses have the "right" to refuse server to anybody for ANY reason they like as long as they clearly post a message that declares that they exercise their "right" to refuse service to anyone they choose to. However, they MAY be subject to someone's (someone they deny to serve) lawsuit IF someone believes they were denied service on the basis of a protected (by Law) class of people. At present, I believe that applies to discrimination on the basis of race, color, or religion. I don't think (yet) the Law's protection applies to sexual orientation. Maybe things have changed in some states but Federally I think that's the present state of the Law.