Rule 9-1-3g was revised in 2014-15 to allow a player occupying a marked lane space to enter the lane on the release of the ball by the free thrower. As a result of this change, protection of the free thrower needs to be emphasized. On release of the ball by the free thrower, the defender boxing out shall not cross the free-throw line extended into the semicircle until the ball contacts the ring or backboard.
The above statement is from the 2015-16 points of emphasis power point. Nowhere in the rule or casebook can I find any statement that says that when boxing out the free thrower a player cannot break the free throw line. So, this point of emphasis is based on the fact that 9-1-3g says that players occupying marked lane spaces can step into the LANE and apparently not behind the free throw line until the ball hits the rim or backboard.
In the early season, some officials have found “tough sledding” when trying to enforce this point of emphasis. The problem is that it requires an official to focus on two areas at the same time that are fifteen feet apart. I am speaking of the free throw line and the rim.
The player boxing out the free throw shooter cannot touch the line or anywhere behind it until the ball hits the rim. It is a difficult ruling to see both actions at the same time. I suggest that you save your whistle for the really obvious.
I also suggest that instead of trying to “knit pick” this free throw violation, officials may be better served by being aware of any illegal contact that the opponent might inflict on the shooter behind the line.
In the past couple of years, we have seen the occasional “butt” displacing the shooter as well as the player boxing out trying to step on the toes of the shooter. Charge personal fouls in these situations.
Below is a clip showing a player who occupies a marked lane space step on or behind the free throw line at about the very instant the shot hits the rim. It is too close and too difficult to call in my view.