It can be done somewhere in this mess:
42 U.S. Code ยง 212 - Retirement of commissioned officers
(c)Recall to active duty
A commissioned officer, retired for reasons other than for failure of promotion to the senior grade, may (1) if an officer of the Regular Corps entitled to retired pay under subsection (a) or under section 213a(a)(19) of this title, be involuntarily recalled to active duty during such times as the Commissioned Corps constitutes a branch of the land or naval forces of the United States, and (2) if an officer of either the Regular Corps or Ready Reserve Corps, be recalled to active duty at any time with his consent.
We had a mustang O-5 retire (30 years) when accused of conduct unbecoming an officer (an affair with an E-4s wife). The investigation revealed enough concern that sexual assault and rape charges were preferred. He was recalled to stand a general courts martial and was found guilty of conduct unbecoming only. He was demoted to O-3 then he retired at the lower grade.
I think with his 30 years in he was not in the ready reserve. It was messy all the way around and the Air Division commander wanted to nail him because of the negative public image it presented.
Your O-5 may have committed this crime while on active duty, I presume, which makes it logical that he could be called back for court martial. I still wonder about a retiree who is already released from ready reserve and out for say, two decades (y’know, just asking for a friend). Your excerpt from the code (thanks, btw), as I read it, does say a Regular Army officer, retired, can be recalled to active duty to be punished for calling some doofuses doofuses. If they don’t go after Kurt Schlichter, though, they are not likely to go after anybody. If they do take on the Vodkapundit, they’ll surely have their hands full. Love to see his column almost certain to come about just this issue.