Delayed Violation?
 

A-1 is at the Free Throw line for 2 throws. While A-1 is holding the ball, B-1 steps in to the lane. The administering official inadvertently sounds the whistle. The official re-administers the the first free throw which is unsuccessful. The official awards A-1 a substitute free throw. Is the official correct?

yes. I think theres a case play where the violation lasts through a TO, so it certainly lasts through an IW.

By rule, you still enforce the violation.

NFHS 6.7.5 SITUATION:

A1 is at the free-throw line for the second of two attempts. After the ball is at A1's disposal, B1 commits a lane violation. The administering official inadvertently sounds his/her whistle: (a) before A1 starts the free-throw motion; (b) after the ball has been released; or (c) during A1's motion but before release of the ball.

RULING: Whether or not the whistle was sounded inadvertently it has the same result. In (a) and (c), the ball becomes dead immediately. In (b), the whistle does not cause the ball to become dead until the free throw ends. Because B1 violated, in all cases, a substitute throw is awarded if the free-throw attempt by A1 is unsuccessful. (4-20-3)