The Chief Justice offers some hints for a future challenge.

CHIEF JUSTICE ROBERTS: I suppose there 11 might be people out there with their own personal 12 standing, someone who performs marriages and would like 13 that to remain open to everyone but would prefer not to 14 perform same-sex marriages, or other people. We seem to 15 be addressing the case as if the only options are the 16 proponents here or the State. I’m not sure there aren’t 17 other people out there with individual personalized 18 injury that would satisfy Article III.

Eugene Volokh has blogged at length about a New Mexico case involving photographers penalized for not shooting a same-sex wedding. This may be an interesting intersection of Free Exercise and Equal Protection.