Emery spoke of the captain's decision not to travel with the squad after their friendly win over Colorado Rapids.
The manager stated, "He started training with us this pre-season and I spoke with him three times for his situation. We wanted him to come with us on this tour but he decided to stay. Now it is a matter for the club and for the player.
"He has one year left on his contract. For me as a coach he's an important player. Now it's one matter for him and the club. The club and him need to speak, they are speaking about his situation. I cannot say more than that. I spoke with him before he came here and he decided to stay there.
"We spoke with a good spirit for both the team and him but this is his decision, only his decision. He's speaking only with the club."
Emery added: "Really I cannot say more about that. For me now it's clear we need to keep moving ahead. We're here with the players who have the spirit to create the new way. Laurent Koscielny for me, now, I'm waiting on his decision with the club."