What FAR says you can't land "off airport"?

I really don't know, but people have received enforcement actions for
landing at closed fields, without an emergency, accidentally, in my
area. They were usually mistaking the larger, closed field for the
smaller, open field on the other side of a river.

I have a feeling there's off-airport, and "closed" airport.

Perhaps the violations weren't of FAR's?

I wonder how the sailplanes handle their landouts ...