sideline and defensive position

[bballref3966]

It is a violation (not a technical foul) to leave the court for an unauthorized reason. I would not consider planting a foot on the sideline to violate this rule.

However, you are correct that legal guarding position cannot be established if the defender has a foot out of bounds. A defender cannot draw a "charge" if he is out of bounds.

[Adam]

LGP must be established with both feet down in bounds. Putting a foot out of bounds would eliminate LGP. In general, this is interpreted to mean a player with a foot out of bounds is not in legal position and, even if he's standing still (thus not normally requiring LGP), he is still at risk of a blocking foul. This would be clearer if the rule makers would add the provision to the screening rules.
The offense could still commit a foul here (pushing or holding, for example), but probably not a charging foul.

[Freddy]

Originally Posted by bballref3966

. . . I would not consider planting a foot on the sideline to violate this rule. . . .

What you would or wouldn't do aside, by rule could you?

[bob jenkins]

Originally Posted by Freddy

What you would or wouldn't do aside, by rule could you?

I don't believe it's the intent of that particular rule.