Yesterday, Justice Kagan asked about what bingo is:

There seems to be dispute whether this type of bingo by machine is the same as the bingo we know, people in a room calling out numbers.

p. 18, line 25 — p. 19, lines 1-3

In a colloquy with the tribe’s counsel, the Chief Justice also wondered aloud:

CHIEF JUSTICE ROBERTS: What would — what — what would you say it looks like?
MR. MARTIN: I would say it looks like an electronic bingo machine that has a bingo —
CHIEF JUSTICE ROBERTS: What makes it look like a bingo machine?
(Laughter.)
MR. MARTIN: Well, there’s a — let me
CHIEF JUSTICE ROBERTS: There’s a name on it that says bingo?
MR. MARTIN: Well, there’s actually a card and you can switch the cards by pushing a button to change the cards that you’re playing. Now, are there reels and lights that look — that would characterize —
CHIEF JUSTICE ROBERTS: Are there people —
MR. MARTIN: — people would characterize it — yes.
CHIEF JUSTICE ROBERTS: — calling out numbers and — people, somebody saying, you know, B-12 or —
MR. MARTIN: There — there in fact is part of our operations, Your Honor. My tribe’s operations is live-called bingo and it’s also one of the things the State of Texas —
CHIEF JUSTICE ROBERTS: But that’s something different than the slot — slot machine bingo, right?
MR. MARTIN: It is different than the electronic machines, Your Honor, but they’ve complained about all of it.

p. 22, lines 4-25 — p. 23, lines 1-11

The law of these bingo slot machines has effectively been settled for nearly 20 years after the Supreme Court denied cert in a pair of petitions from the United States on this question (which later led to regulations that effectively codified the rulings from the courts below that the government lost):

What is Class II bingo, a Supreme Court Justice might ask? Well, the General Counsel for the National Indian Gaming Commission is there to offer answers: