I would think it applies to attendees and not necessarily to speakers. Like a conference on I dunno, Brazilian businesses, maybe they only want Brazilian speakers --I can'[t imagine there be a requirement for there to be any American speakers or any class.

> Like a conference on I dunno, Brazilian businesses, maybe they only want Brazilian speakers

AFAIK there's an exception if it's vital part of the job, like in that case (a conference about Brazillian businesses I presume). I was thinking more like, a node.js conference where you say "no muslim speakers allowed".