Sideline position?
 

Looking for rule pertaining to defensive positioning on this play: A1 is advancing ball up sideline in backcourt. B1 takes a position (established) in front of A1, but with one foot on out of bounds line. Contact then occurs when A1 attempts to go around B1, but does not have enough room without going out of bounds himself. Is it legal or not for B1 to have the one foot oob?

B1's position is not legal, making him liable for a foul for any contact. Being inbounds is a condition of both acquiring and maintaining LGP. 4-23-2, 3

Here we go again. B1 does not need LGP if he isn't moving, except maybe in this one case play.

I've got him legal if he's stationary. Others have a block regardless.

If the defense has one foot out of bounds and one foot in bounds, I and every official I know here has a block on any contact.

Case Book

4.23.3

A1 is dribbling near the sideline when B1 obtains legal guarding position B1 stays in the path of A1 but in doing so has (A) one foot touching the sideline......

Ruling: In (A) B1 is called for a blocking foul because a player may not be out of bounds and obtain or maintain legal guarding position.

I really don't understand why this is difficult. If a defensive player is on the line or out of bounds and there is contact it is on the defense.

Not every foul is about legal guarding position. B1 is standing near the bench, getting instructions from his coach. It just so happens he has one foot on the line. Dribbler A1 comes down the sideline and plows into B1.
B1 is stationary. B1 has done nothing wrong. This is not a foul on B1.

Then it is a violation on B1 for leaving the court under is own voilition?

The rule says B1 is entitled to his spot on the court. He's either entitled to this spot, or he's not on the court. IMO, if one foot on the line isn't enough to call the violation for leaving the court, then a stationary B1 isn't liable for the contact.

That is a totally different situation than what the OP is addressing.

How is it different, by rule?

4-37-3

Every player is entitled to a spot ion the playing court, provided the player gets there first without illegally contacting an opponent.

They key phrase is playing court. One foot out of bounds means they have no position on the court.

Not really.

Fair enough. I just know how I will call this and how I have called this, and I have never had a problem from a coach when I explained it to him.

His spot is not on the court, since by rule his location is not inbounds.

I agree that this position is insufficient for a "leaving the court" violation (9-3-3), but I disagree with your reasoning back to having a spot on the court.

The reason a toe on the line not sufficient for the LTC violation is that touching the boundary alone does not constitute leaving.

It does, however, constitute a player being OOB, and thus denies him a legal position on the court. He is not entitled to that spot, and so liable for any contact.

Like I said, unless you're willing to call the violation for leaving the court, I don't think you can say B1 has left the playing court. IOW, you either have a defensive violation (thus an immediate dead ball), or a pc.

How did he get off of the court if he didn't leave?