Go check out this cartoon from Cox and Forkum.
My dad retired from the Marine Corps in 1984, but he still has quite a few friend who are still somehow involved with the Corps. He's also in the Marine Corps League (they do the Toys for Tots every year at Christmas, as well as several other ceremonial functions).
After September 11th, when I was having a long discussion with my father, he told me about a retired Marine Major who called up Marine HQ (on I St. and 8th) in Washington D.C. and told them that he wanted to re-join. The Marine on the other end of the line was somewhat surprised, but took down the Major's name and info, and then put him on hold while the information was relayed to someone higher up.
After about ten minutes, another Marine picked up the phone and told the Major "I'm sorry sir, but your status is 4-I right now, we're unable to take you back." The Major was rather put out, and demanded to know what 4-I status actually was. He was told "When the Enemy is at the intersection of 4th and I St., you'll be getting a call."
By the way, the Major was a Viet Nam vet around 60 years old. Heh.
It just reminded me that there are a lot of people who want to rejoin, re-enlist, re-up, what have you, but due to age or other physical conditions, they've been told "No". Plus, the story (and the cartoon) gave me a little chuckle.