Backcourt Violation on a Steal

Q3. After a made basket, my team (team A) was pressing team B in the backcourt.  Player B2 received the ball at his backcourt, B2 attempted a long pass to his teammate B1 in the frontcourt, and the ball was stolen by A1 jumping off from our front court and landed with 1 foot on our backcourt. The referee blew the whistle and called a backcourt violation.  Was the
call correct? Can a team establish frontcourt position without having possession of the ball?

A: In pure answer to your question, the player has status wherever his feet were last touching on the court for the offensive, whether they have possession in the frontcourt or not. But, there is a provision for the defense when they make a good defensive play. It is referenced in this article in the rulebook (the last part of the second bullet point covers it):

30.1.2 A team in control of a live ball in the frontcourt has caused the ball to be illegally returned to its backcourt, if a player of that team is the last to touch the ball in his frontcourt and the ball is then first touched by a player of that team: 

• Who has part of his body in contact with the backcourt, or 
• After the ball has touched the backcourt of that team. This restriction applies to all situations in a team's frontcourt, including throw-ins. However, it does not apply to a player who jumps from his frontcourt, establishes new team control while still airborne and then lands with the ball in his team’s backcourt.

So what you describe above is not an infraction.