For a BC violation to occur, 4 criteria must be met.
1- Team A must have team control:
a- In rules lingo, Team A is always the team with the ball.
b- To establish team control, a player must be holding or dribbling the ball inbounds.
2- The ball must attain FC status:
a- This means the ball must touch something, anything in the FC.
b- It is not necessary for Team A to touch the ball in the FC, for FC status to be established.
3- Team A must be the last to touch the ball before it goes into the BC.
a- Again, this does not mean that A has to touch the ball in the BC.
b- If A1 is standing in the BC, passes the ball, hits an official in the FC, and bounces back into the BC, it would be a violation if A1 touches the ball.
4- Team A must be the first to touch the ball after it has been in the BC.
a- This does not mean that A has to touch the ball in the BC.
b- If A1 is standing in the FC, bounce passes the ball to A2 and the ball hits the division line, it would be a violation when A2 touches the ball.
If all 4 criteria aren't met, no violation.
Pretty simple, huh?