It is amazing to me how people react so strongly to the characterization of banished and yet jump to the worst possible conclusion about the nature of the husband's behavior. There is nothing in the OP that makes it sound like he was marking his territory or asserting dominance or any of the odd descriptions posters have jumped to over the course of five pages of discussion.
And I'm sorry - dislike of the term banished aside - if there is an understanding that him sitting in a common area of his home and speaking to guests (or there is a time limit to such behavior) then he is being banished. The fact that is doesn't happen right away doesn't change the expectation that he either cease participating or leave.
I'm glad a couple of posters have pointed out that they too would be uncomfortable with a mandate of little to no presence of their spouse while hosting people in their homes, but deeply distressed that later posters again jumped to assumption that he was being willfully rude (as opposed to playful) and that there is some marital issue at play here.
At the end of the day, at least, the OP has gotten cogent advice from posters on both sides and the solution appears to be the same - talk to Amy, explain the "rules" and let her make the choice on how to deal with it.
The thing is, Amy knew the rules. She's been to 6 such events, and openly stated that she knew her husband wasn't supposed to be around. Casually assuming that the rules don't really apply to you is rude. Of course, Amy is free to dislike the rules, but, you know, she wasn't conscripted into this bunco club.
Sometimes my wife has get-togethers with her old school friends. I understand complete that I am not welcome at those events, even if they are hosted in our home. There's a specific vibe that they want to have, and including somebody not from that original group alters the vibe. I get it.
It doesn't mean that I have to be like Harry Potter at the Dursleys', making no noise and pretending I don't exist, it just means that I hang out in another room for a few hours. If I need something from the room where they are, I can get it, and I'll say hi, but I won't attempt to include myself in their gathering. Certainly if I had an issue, I'd raise it with my wife beforehand. I wouldn't be a big baby and try to force the whole situation to bend to my will. And if my wife felt uncomfortable excluding me for the evening, the right thing to do would be to be honest with her friends, not to try to passive-aggressively alter the nature of the event.
Amy and her husband get no passes from me. The group is what it is, accept that, or go elsewhere for bunco. Is that really so hard?