On using a modifier with a (comma-separated) list

Solution 1:

1: Due to the lack of a comma after "auditoriums", it would seem, in basic grammar and sentence flow, that "when used" refers to "auditoriums"; but, by the same logic, the exceptions could only be applied in the auditoriums. If so, perhaps they can only limit photographs in certain areas in the first place.

2: Yes. Don't put the item with the modifier at the end of the list. Another, more complicated, answer is to use semicolons in your list, making the item separations stronger and more specific, and a comma after "meetings", or, if the exceptions apply to the common areas, a period after "meetings", followed by "Restrictions will apply when...".