the ball is in court

the ball is in (one's) court

One needs to take some action to keep something going. 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?
See also: ball, court

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.
See also: ball, court