When the NCAA used the "no charge" semi-circle early in the season as an experimental rule, what is the call for a stationary established defender inside the semi-circle that clearly is charged into by an offensive player? Is it automatically a blocking foul or could it be a no call.

by rule - you have two options as an official: block or no-call.

While I like the intent of the rule - don't reward the defense for playing defense under the rim; the exact play you bring up makes it hard to officiate (at least until the defense is "trained" not to take a charge under the rim).