the ball is in court
the ball is in (one's) court
One has the responsibility for further action, especially after someone else previously held responsibility. The phrase originated in tennis. Well, they invited you, so the ball is in your court now. Do you want to go out with them or not?
the ball is in someone's court
Fig. to be someone else's move, play, or turn. (From tennis.) The ball's in your court now. You do something. I can't do anything as long as the ball is in John's court.