I'm trying to figure out some rulings for several silver-bordered cards, and I came across a black-bordered scenario I can't find an discussion of. I think I've answered my own questions, but I'd like to share my thoughts.

Suppose a player in a three-player free-for-all game attacks with a band of two creatures with banding. All creatures in an attacking band must be attacking the same player or planeswalker, so at first they're all attacking one opponent. That opponent casts Portal Mage in the declare attackers step, reselecting for one of the two creatures to attack the third player.

The rules for Portal Mage mention nothing about bands. In fact, they even say the reselection can ignore attacking restrictions -- which isn't to say the band homogeniety thing is an "attacking restriction" in quite the same sense as Blazing Archon.

If this kind of surgery on bands is allowed... well, maybe there's nothing wrong. I thought there'd be a problem if multiple players blocked with banding creatures, or if multiple defending players controlled Defensive Formation, but no, in those cases each attacking creature's outgoing damage is assigned specifically by the player it's attacking. There's no ambiguity.

What do you think?

Your explanation seems clear to me. I'll check the rules carefully later, but if the answers are that unambiguous, they are correct, even if they are weird.

I just noticed General Jarkeld, which makes it more clear that a blocking creature doesn't necessarily have to be controlled by its attacking creature's defending player. Combining that with Aetherplasm or Flash Foliage demonstrates that a creature can be blocked by two creatures with different controllers, so this Portal Mage+banding scenario is not the only scenario of its kind.