Moving screen?

[egausch]

Ok, saw this recently, pretty typical sitch. Three player fast break, A1 on right w/ ball, A2 in middle, B1 on left, all spaced about 5 ft apart. Layup goes in but whistled off "moving screen"(might be better called as an illegal screen or illegal moving screen). Seems like the correct call. But here's the rub. B1 made absolutely no attempt to play the ball. B1 and A2 ran parallel paths all the way to the hoop. Does it matter? What if the spacing was larger? Does time and/or distance matter? Is this an advantage/judgement call or is it black and white. I've always taught/coached my players to set stationary screens and they can't move to block the defender. It's up to the screener's teammate to move to use the screen correctly. The screener must also keep all parts of his body within his defensive box. So, for this moving sitch, it seems I should coach my guys, when A2, to pull up and follow the play as a trail, etc., to avoid the call.
EG