The New Jersey Nets have taken a similar step.
Arenas and teammate Javaris Crittenton reportedly pulled guns in Washington's locker room during a recent dispute over a gambling debt on a team plane.
Stern said Arenas was "not currently fit to take the court in an NBA game."
"David Stern is not taking this lightly, but we need Gilbert," teammate DeShawn Stevenson told the Post Wednesday.
Arenas and teammate Javaris Crittenton reportedly pulled guns in Washington's locker room on a team charter last month.
The team added fines will be assessed against any player who laughed when Arenas mocked a gunshot before Wednesday's 121-98 loss at Cleveland.