Short answer. Three members constitute a quorum for a division's sessions, and the affirmative votes of three members of that division are needed to pronounce a judgment or final resolution, which must first be reached in consultation before any member writes the opinion.
What the law says
A majority of the actual members of the court shall constitute a quorum for its sessions en banc. Three members shall constitute a quorum for the sessions of a division. The affirmative votes of the majority of the members present shall be necessary to pass a resolution of the court en banc. The affirmative votes of three members of a division shall be necessary for the pronouncement of a judgment or final resolution, which shall be reached in consultation before the writing of the opinion by any member of the division.
Rule 54, Section 2 — Quorum of the court. Read the full provision →
Two different quorum rules
Rule 54, Section 2 sets different quorum requirements depending on whether the Court of Appeals is meeting en banc or as a division. For en banc sessions, a majority of the court's actual members is needed. For a division — the body that actually hears and decides most appealed cases — the quorum is fixed at three members, regardless of how many justices sit on that division in total. Because divisions typically consist of three justices, this quorum rule effectively means all three ordinarily need to be present for the division to validly conduct business.
Voting requirements track the quorum structure
The voting rule follows the same split. En banc resolutions pass with the affirmative votes of a majority of the members present at that session. For a division's judgment or final resolution, however, the section requires the affirmative votes of three members specifically — not merely a majority of whoever happens to be present — before the ruling can be pronounced. This fixed three-vote requirement means a division cannot render a valid judgment with only two justices agreeing, even where a temporary vacancy or absence leaves fewer than three sitting at that moment.
Consultation comes before the written opinion
The section also requires that the division's judgment or final resolution be reached in consultation among the justices before any one of them writes the opinion. This sequencing matters: the writing justice is expressing a decision the division has already agreed upon in consultation, not proposing a draft that the others then vote on afterward. Requiring consultation first also means the eventual opinion can be drafted knowing the outcome and the reasoning the division has already settled on together, rather than the writing justice having to guess what will ultimately command three affirmative votes.