My understanding is anyone can be sued for pretty much anything. But I suppose the intent of the question is "can they win if they sue?". And that depends on what they sue for. In the Philadelphia case I'd think they could make a claim that they were misled and invested money and time on the reasonable assumption that they were welcome. It's doubtful the club had the balls to make their racial policies explicit, so there's breath of contract possibilities.

I'd think they could definitely sue. Maybe not for "discrimination" per se, but for getting screwed around by vague and unpredictable policies. Of course, in terms of reversing the policy, the more effective tact might be to just to expose the club publicly, and relentlessly, as the backward asshats they apparently are.