Supreme Court Justice Stephen G. Breyer, center, waits for then-President Barack Obama’s arrival for the State of the Union address on Jan. 28, 2014, at the Capitol. (Bill O’Leary/The Washington Post)

Turns out that cellphones are allowed in the grand courtroom of the Supreme Court — so long as the holder is a justice.

The unmistakable sound of a cellphone ringing interrupted Tuesday morning’s argument in Bristol-Myers Squibb Co. v. Superior Court of California, followed by a scramble on the part of Justice Stephen G. Breyer. The embarrassed-looking justice moved quickly to stop the sound, while some of his colleagues smiled and looked at the ceiling.

Electronic devices are strictly forbidden in the courtroom, even for the lawyers who are arguing cases. Visitors must leave cellphones in lockers and go through metal detectors before entering.

Some questions about today’s incident remain unanswered. Breyer’s ringtone was not the usual sounding one, but reporters couldn’t make out exactly what it was. And it is unclear whether a justice’s black robe has pockets.