Is this correct? (NFHS)
 

A1, holding ball in-bounds, contacts A2 or B2 who are out-of-bounds: legal.
A1, holding ball out-of-bounds for throw-in, contacts A2 or B2 in-bounds: violation.

Just learned something here. I didn't know this was illegal. Why is this only mentioned in a note rather than being worthy of an article?

#1...correct. Touching a player who is OOB doesn't make A1 OOB.

#2...incorrect. While it appears that it is a violation for the throwER (correction) to touch a teammate (thanks for the tip JAR...didn't know that either). B2 presents a dilemma. As of this year, contact with a thrower by a defender is an intentional foul....but here we have a rule that says it is a violation. Hmmm.

I assume you meant thrower.

Doesn't seem to be any difference in touching a teammate or an opponent. It simply says may not touch a player or the inbounds area.

Violation if A1, thrower, makes contact inbounds with B1. If B1 makes contact with A1, intentional. The new intentional foul rule really makes watch and see who initiates the contact.

I believe the new rule says CONTACT with the thrower is an intentional foul. Before, it didn't matter who initiated the contact, but only if the contact was across the plane....the contact was automatically an intentional foul. They only removed the plane boundary from the equation.

NFHS: "When a defender makes contact with a thrower-in, the result is an intentional foul."

Making contact is not the same as causing contact.

Also, that interpretation was written in the context of the defender slapping the wrist/arm of the thrower, but similar such statements (see LGP and a player with a foot OOB) have often been read as being absolute and applying to all contexts.

I actually do NOT like it. I think that if the ball is across the line and the ball is fair play, then a foul that occurs on the attempt to legally play the ball should be a normal foul...the rule change was a bad rule change.

Here is a situation I can see happening.

Team A is down 2 points, with 10 seconds left in the game. A1 reaches across the endline and starts moving arms in a circular motion and contact happens with B1 as a result. Intentional foul by B1. Team A gets 2 free throws and the ball. I dont think this was thought out very well. Is it a violation when A1 broke the boundary plane?

No. A1 is not restricted from breaking the plane.

This would be a nightmare situation.

In Referee Mag this month...
 

... page N15,
Losting balance on a throw-in

Play: A1 is holding the ball for a throw-in. Prior to releasing it, A1 loses his or her balance, reaches out and touches B2 who is standing inbounds and guarding A1 on the throw-in. A regains balance and completes the throw-in. Is the throw-in legal?

According to 9-2-10 Note: no

Citation ...
 

The thrower may penetrate the plane provided he/she does not touch the inbounds
area or a player inbounds before the ball is released on the throw-in pass. The opponent
in this situation may legally touch or grasp the ball.

Violation

It would be an advantage clearly not intended by the rule. I'm calling a violation on A before I call an IF on B here.