They'd been fighting a war for years. Which was why Remus was enough on the ball to flick the hand without his wand. "Accio wand," he announced, meaning to pull Sirius' wand from his hand.

He didn't know what Sirius was going to do. But taking his wand limited what Sirius COULD do, at least magically. "Sirius. Sirius, no. You can't kill him."

Oh Merlin. If Sirius was right...and what reason did he have to disbelieve him? It was the smart thing to do. Everybody knew that Sirius would be James' secret keeper. So it would have been smarter to use somebody else.