Kings in the SCA can canonise people? Impressive.
Hey, if Henry VIII could decide to create his own church...
The SCA is religion-neutral, so there aren't any popes. Since
somebody has to do these things, it might as well be the kings (or queens; some women enter the lists, win, and become Queen in their own right). Besides, it's clearly understood that the persona of Geoffrey Whoever-he-was (I never did know the rest of his real SCA name) had been canonized. The person who portrayed St. Geoffrey of the Hot Tub had no claim whatsoever to sainthood in his mundane life.
On a much lesser scale, in my SCA life I'm minor aristocracy, having been granted an Award of Arms and the right to be addressed as "Lady." Of course this has no bearing on my mundane life.
Kings and Queens reign for only 6 months, btw (they spend 6 months after winning the tournament learning the job; they're known as the Crown Prince/Princess, and after that they take over from the outgoing monarchs). Crown Tournaments are held every 6 months. Most decrees such as canonizing someone are upheld by future monarchs as a matter of courtesy, unless the decree results in problem situations or was always intended to be just temporary.
I remember one decree that stated that we weren't allowed to refer to our costumes as costumes; we had to say "garb" - and we weren't allowed to call our cars or trucks by any other word except "wagon." Of course in our local part of the Knowne World, we shrugged, said, "We don't care; we'll do what we always do" and ignored it (same as when the Board of Directors in California decided that weddings could no longer be celebrated since they were deemed to be religious activities; we basically said, "Screw the BoD, we're having weddings anyway").