Groups with Requirements of membership in other organizations.
 

I was looking at the group Clovia (https://en.wikipedia.org/wiki/Clovia_(sorority) ) that apparently requires pre-college membership in 4-H. Alpha Phi Omega from 1925 (Founding) until 1967 required (more or less) prior membership in Boy Scouts of America. Omega Phi Alpha from 1953 (founding) to 1958 required membership in Girl Scouts or Campfire Girls.

Masonry was required originally for membership in Acacia (1904-1931/1933) and Phi Omega Pi (which sort of merged with Delta Zeta) started out with requiring (1922-1933) that the women be members of the Order of the Eastern Star.

Any ideas for other Fraternity/Sorority/related that require or required membership in other organizations before you could join?

(And I wonder if you could set up a Professional or Honorary that would theoretically be open to both genders, but require pre-college membership in a group that is single gender, that might be interesting to deal with in court)