Hmmmm, a reverse "legacy"...
Well, "an old fart like myself could become a member of your fraternity" like every other brother does; in a super double secret ritual involving butter, farm animals and some certain photos that our beloved Tom Earp thought no longer existed (I had doubles made Earpski!)
In all seriousness, I believe that you must currently attend a college/university to qualify as an "Associate". However, there have been exceptions made and many gentleman in your like position have been granted honorary membership, such as Harry Truman.
Maybe one of our scholars can correct me, but I always thought that no matter how you become a member, either the traditional or non-traditional way, that you MUST go through ritual/initiation?
Anyways, your best bet is to contact Headquarters directly,
www.lambdachi.org. Although don't hold your breath for an immediate response. Answers can sometimes come...rather slowly...depending on the time of year.
I am the first to respond, but don't worry, you've come to a virtual museum or library of Lambda Chi Alpha knowledge and one of our regular posters will be able to answer your question.