Images of living persons cannot be on USPS-issued postage stamps.
Debate the use of "living" as it applies to Barker, if you must. Or "person," for that matter.
Or "cannot".
I believe this was the first time. It has happened a number of times since. Here is a more recent example. See if you can figure out what other thing the two stamps have in common.
The way I read the "living person" definition for USPS-issued stamps is that if the stamp is actually acknowledging the person on the stamp by name, they must be deceased. In the case of the "Heroes" stamp, and other stamps denoting specific events, places or organizations, they can use a living person's likeness, but cannot identify them by name.