When does the ball gain BC status? When it touches the floor or any person that is on the floor in BC? Who is the first to touch it? Both things occur simultaneously. The ball gained BC status when touched by A1 who was standing in the BC. And A1 was the first to touch the ball once it has gained BC status. B may have been the last to touch it, but it did not change team control when he touched it.

4-4-3 A ball which is in flight retains the same location as when it was last in contact with a player on the court. [In this case, B was in the FC and touched it].
4-4-4 A ball which touches a player or an official is the same as the ball touching the floor at that individual's location. [In this case, A's touch of the ball in BC gave it BC status. Not B's touch in the FC. A was the first to touch it after it was given BC status by virtue of A's touch. They occurred at the SAME TIME.]

By your reasoning regarding causation, he must have, as he causes the ball to gain BC status when it hits his leg. Fundamentally, it's identical to the interp.

What else could it mean? Exactly what it says; perhaps worded slightly differently, "gained backcourt status."

And B was the last to touch the ball before it went into the backcourt.

OK, I'll come clean: the interp is flawed in supposing that the touching by A and the ball gaining backcourt status are distinct events. If they were distinct, it might make sense to say that the former causes the latter. But they're not.

Without getting too metaphysical, the touch by A does not cause the ball to go to the BC, it constitutes the ball gaining BC status. The touch just is the ball gaining BC status. I think this is the idea people are reaching for when they say that the "two" events are "simultaneous." I would like to tell the committee that you don't have two events here at all: just one event, with two ways of describing it. One description is about touching, and one is about the status of the ball.

That's why "cause" is inappropriate for the interpretation of "went to the backcourt." Without two distinct events, you cannot possibly have cause and effect.

And so when A is in the BC and touches the ball, A is NOT the last to touch before the ball went to the BC. No violation.

A1 releases the ball on a throw-in attempt. B-1 a. deflects ball to A1 who catches it or touches the ball while still standing out of bounds. b. touches the ball while standing out of bounds after B-1's deflected ball hits the floor. c. deflected ball hits the official who is standing out of bounds and then is touched by A1 who is still standing out of bounds.

When is the ball out of bounds? Whose violation is it? Will this horse ever live again?

Different rules, as the OOB violation is for "causing the ball to go OOB." That's not the case for backcourt.

Not if I can help it.

Not really. If A lets the ball hit the floor, there is no violation. Same in the BC case play.

Mickey Mantle took Billy Martin to a friend of his in TX to do some deer hunting. Billy had always managed to put Mickey on the wrong end of practical jokes. Mickey told Billy to wait outside while he went in to ask permission. Mickey's friend said he could hunt under one condition. He had a mule that needed to be put down and he didn't have the heart to do it. If Mickey would do it, he could hunt.

He went outside and without saying a word, plucked out his rifle and headed to the pen. "What'd he say?", asked Billy. "He said 'no'", Mickey replied and he proceeded to put down the mule with a single shot. Mickey then hears "Blam! Blam! Blam!" and turns around to hear Billy exclaim, "Let's get out of here, I just got 3 of his horses!"

Also....

If causing the ball to have BC status were the violation, we'd blow the whistle the moment the ball bounces in the backcourt even if it was not yet touched. But it is not and we don't.

The difference lies only with the reasoning of the interp; a faulty reliance on the term "cause," which is not in the rule.

Causing the ball to gain BC status is not a violation.

Correct...but irrelevant.
Correct.
Correct...but irrelevant.
Correct...but irrelevant.

The real question is who was the last to touch the ball BEFORE it gained BC status. If it was A, violation. If it was B, no violation.

Irrelevant...loss of team control is not necessary for A to retrieve the ball in the BC.
Agree...and that is why it should NOT be a violation when B was the last to touch the ball before the ball goes into the backcourt (whether it bounces or not before A touches.
Agree.
It doesn't have to be touched in the frontcourt to end the count...the count can also end if the ball merely bounces in the FC.

However, this is also not relevent. The 10 second count is about the status of the ball...nothing more. The BC violation is about who touched the ball before and after the change in status of the ball from FC to BC.

Who's the guy in white riding Chuck?

Or is He riding some other donkey?

You don't remember him? He's the one who spit in the dirt and put the mud in your eye to help you see.

I see.

Exactly. Then he told you to shut up.