Historical Rules · 25 August 2017
Rule 702.21c
Official source text from the 25 August 2017 Rules release
As a player declares attackers, he or she may declare that one or more attacking creatures with banding and up to one attacking creature without banding (even if it has “bands with other”) are all in a “band.” He or she may also declare that one or more attacking [quality] creatures with “bands with other [quality]” and any number of other attacking [quality] creatures are all in a band. A player may declare as many attacking bands as he or she wants, but each creature may be a member of only one of them. (Defending players can’t declare bands but may use banding in a different way; see rule 702.21j.)