I wondered the same thing a while ago and my understanding is that these are all covered by the Civil Rights Act of 1964[1][2]. The gist is there's not so much

I wondered the same thing a while ago and my understanding is that these are all covered by the Civil Rights Act of 1964[1][2]. The gist is there's not so much a line you can't cross, but rather that what is illegal is explicitly enumerated. The act defines what specifically is a protected class (sex, race, religion, and so on) and a number of specific situations where it is not permitted to discriminate against members of those classes (e.g. employment, schools, access to public spaces like restaurants and theatres, etc.) So in your examples I believe the answer is yes, single-sex clubs are permitted so long as they're private clubs. A scholarship that only members of a single sex are eligible for is also allowed since that's not one of the things the act covers. I think a VC firm that only backs founders of a particular sex is also legal since that's investment rather than employment. An Outstanding Male Award would be legal (and I can't really think of any ethical reason that'd be a problem.) A White Male Study Room would probably _not_ be legal presuming we're talking about a public facility, however to expand on that concept a bit, I _think_ a private school for white males _might_ be legal. Title IV appears to be the relevant portion, which doesn't as far as I can tell apply to private schools so long as they don't receive any sort of public funding for research or other purposes. [1] https://en.wikipedia.org/wiki/Civil_Rights_Act_of_1964 https://en.wikipedia.org/wiki/Civil_Rights_Act_of_1964 [2] https://www.ourdocuments.gov/doc.php?flash=true&doc=97&page=transcript https://www.ourdocuments.gov/doc.php?flash=true&doc=97&page=...