Rule 10, Art 5, Subsection A says repeatedly delaying.......so if its the first time, I would say, yes you can warn them. If they continue to do this, its a T. Did they get confused on the throw in?
After a team warning has been issued, repeatedly delaying the game
by preventing the ball from being promptly put in play, such as
delaying the administration of a throw-in or free throw by engaging
in a team huddle any place on the playing court.