We run into the same thing this weekend, batters moving up in the box.
Coach tells catcher to move up and she doesn't. Catcher says she did but umpire told her she had to stay behind the batters box.
I tried to find the rule but couldn't find. What is the rule, please?
Don't have the rule number or rules supplement number handy at the moment. The rules do state the catcher must be in the catchers box but it does have an exception when the batters are up in the front of the box. The catcher is allowed to mover forward as long as they do not obstruct the batter. The entire batters box belongs to the batter and they could move back at any time.