Legal "counting" position

[Burtis449]

National Federation Rules.
Offensive player with the ball in the front court in a "trapped by sideline" situation is guarded by a player who has one foot on an out of bounds line. Should the referee be counting for a possible 5 second violation?
Or should there be no count because the defender has a guarding position which is not legal because he/she has one foot on the line!!
I'm using the same logic as the defender who has one foot on the line and takes contact from the offensive player. This is to be called a "block" because the defender is not in a legal guarding position.