Unoccupied lane space

[PSidbury]

Assuming NFHS:

So, where in the Rules Book does it state that the first marked lane spaces must be occupied by opponents of the free thrower?

Rule 8-1-4 states: "During a free throw when lane spaces may be occupied..."

It certainly does not state "when lane spaces must (or will) be occupied"

There is a difference between "you may occupy" and "you must occupy."
The former implies objective discretion, while the latter implies strict adherence.

Again, even 8-1-4b uses the word shall and not must or will be. And even that usage of shall is within the context of 8-1-4: "...when lane spaces may be occupied..." Which seems to say that if you choose (that objective discretion thing) to occupy the lane, then you shall do it a certain way.

Going to need another pair of eyes, because I cannot find clear language that must put an opponent on the first marked lane spaces.

There is clear language, however, that states when players shall not occupy the lane (ie., 8-1-3).

Can't find anything in 9-1 either, other than a reference back to 8-1-4.

Thanks,
Paul